Chemical Reactions & Equations
Q151EasyBPSC Prelims
Which of the following is an example of a combination (synthesis) reaction?
ACaCO₃ → CaO + CO₂
BFe + S → FeS
CZn + CuSO₄ → ZnSO₄ + Cu
DCH₄ + 2O₂ → CO₂ + 2H₂O
Show Answer
✔ B — Fe + S → FeS
Combination (synthesis) reaction: two or more reactants combine to form ONE product.
Fe + S → FeS (iron + sulphur → iron sulphide)
Formula: A + B → AB
Other types:
- A: Decomposition (CaCO₃ → CaO + CO₂) — one compound breaks into two
- C: Displacement/Single replacement (Zn displaces Cu from CuSO₄)
- D: Combustion (CH₄ burns in O₂) — special type of combination/redox
*Why A is wrong:* CaCO₃ → CaO + CO₂ = Decomposition (one → two).
*Why C is wrong:* Zn + CuSO₄ → ZnSO₄ + Cu = Single displacement (one element displaces another).
*Why D is wrong:* CH₄ + O₂ → CO₂ + H₂O = Combustion reaction.
Fe + S → FeS (iron + sulphur → iron sulphide)
Formula: A + B → AB
Other types:
- A: Decomposition (CaCO₃ → CaO + CO₂) — one compound breaks into two
- C: Displacement/Single replacement (Zn displaces Cu from CuSO₄)
- D: Combustion (CH₄ burns in O₂) — special type of combination/redox
*Why A is wrong:* CaCO₃ → CaO + CO₂ = Decomposition (one → two).
*Why C is wrong:* Zn + CuSO₄ → ZnSO₄ + Cu = Single displacement (one element displaces another).
*Why D is wrong:* CH₄ + O₂ → CO₂ + H₂O = Combustion reaction.
Q152EasyBPSC Prelims
Combustion is a type of chemical reaction. Which of the following is always a product of complete combustion of a hydrocarbon?
ACarbon monoxide (CO) and water
BCarbon dioxide (CO₂) and water (H₂O)
CCarbon and hydrogen gas
DOxygen and carbon
Show Answer
✔ B — Carbon dioxide (CO₂) and water (H₂O)
Complete combustion of a hydrocarbon (CₓHᵧ) in excess oxygen:
CₓHᵧ + O₂ → CO₂ + H₂O
- Always produces CO₂ and H₂O (when oxygen is sufficient)
- Complete combustion = blue/clear flame, no soot
Incomplete combustion (insufficient O₂):
CₓHᵧ + O₂ → CO + H₂O + C (soot) — yellow/smoky flame
*Why A is wrong:* CO + water = incomplete combustion (insufficient O₂).
*Why C is wrong:* Carbon and H₂ are not combustion products — these would be decomposition products.
*Why D is wrong:* Oxygen and carbon cannot both be products of combustion of a hydrocarbon.
CₓHᵧ + O₂ → CO₂ + H₂O
- Always produces CO₂ and H₂O (when oxygen is sufficient)
- Complete combustion = blue/clear flame, no soot
Incomplete combustion (insufficient O₂):
CₓHᵧ + O₂ → CO + H₂O + C (soot) — yellow/smoky flame
*Why A is wrong:* CO + water = incomplete combustion (insufficient O₂).
*Why C is wrong:* Carbon and H₂ are not combustion products — these would be decomposition products.
*Why D is wrong:* Oxygen and carbon cannot both be products of combustion of a hydrocarbon.
Q153MediumBPSC Prelims
A redox reaction involves:
ASimultaneous oxidation and reduction
BOnly oxidation of one substance
COnly reduction of one substance
DExchange of protons between substances
Show Answer
✔ A — Simultaneous oxidation and reduction
Redox reaction (oxidation-reduction): both processes occur simultaneously — you cannot have one without the other.
- Oxidation: loss of electrons (or gain of oxygen, or loss of hydrogen)
- Reduction: gain of electrons (or loss of oxygen, or gain of hydrogen)
Oxidising agent = oxidises another substance (itself gets reduced)
Reducing agent = reduces another substance (itself gets oxidised)
Example: Zn + CuSO₄ → ZnSO₄ + Cu
- Zn → Zn²⁺ + 2e⁻ (Zn is oxidised — reducing agent)
- Cu²⁺ + 2e⁻ → Cu (Cu²⁺ is reduced — oxidising agent)
*Why B is wrong:* Oxidation alone doesn't make a redox reaction — something must also be reduced.
*Why C is wrong:* Reduction alone doesn't constitute a redox reaction.
*Why D is wrong:* Exchange of protons = acid-base reaction (not redox).
- Oxidation: loss of electrons (or gain of oxygen, or loss of hydrogen)
- Reduction: gain of electrons (or loss of oxygen, or gain of hydrogen)
Oxidising agent = oxidises another substance (itself gets reduced)
Reducing agent = reduces another substance (itself gets oxidised)
Example: Zn + CuSO₄ → ZnSO₄ + Cu
- Zn → Zn²⁺ + 2e⁻ (Zn is oxidised — reducing agent)
- Cu²⁺ + 2e⁻ → Cu (Cu²⁺ is reduced — oxidising agent)
*Why B is wrong:* Oxidation alone doesn't make a redox reaction — something must also be reduced.
*Why C is wrong:* Reduction alone doesn't constitute a redox reaction.
*Why D is wrong:* Exchange of protons = acid-base reaction (not redox).
Q154MediumBPSC Prelims
In the reaction: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)
What type of reaction is this?
ACombination reaction
BDouble displacement reaction
CDecomposition reaction
DNeutralisation reaction
Show Answer
✔ B — Double displacement reaction
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
This is a double displacement (double replacement) reaction:
- CaCO₃ and HCl exchange ions: Ca²⁺ pairs with Cl⁻ (CaCl₂); H⁺ pairs with CO₃²⁻ (H₂CO₃ → H₂O + CO₂)
- Pattern: AB + CD → AD + CB (with ion exchange)
Also categorised as an "acid + carbonate → salt + water + CO₂" reaction.
*Why A is wrong:* Combination produces one product — this has multiple products.
*Why C is wrong:* Decomposition requires one reactant breaking down — this has two reactants reacting.
*Why D is wrong:* Neutralisation is acid + base → salt + water. CaCO₃ is a salt (not a base), though it does neutralise the acid.
This is a double displacement (double replacement) reaction:
- CaCO₃ and HCl exchange ions: Ca²⁺ pairs with Cl⁻ (CaCl₂); H⁺ pairs with CO₃²⁻ (H₂CO₃ → H₂O + CO₂)
- Pattern: AB + CD → AD + CB (with ion exchange)
Also categorised as an "acid + carbonate → salt + water + CO₂" reaction.
*Why A is wrong:* Combination produces one product — this has multiple products.
*Why C is wrong:* Decomposition requires one reactant breaking down — this has two reactants reacting.
*Why D is wrong:* Neutralisation is acid + base → salt + water. CaCO₃ is a salt (not a base), though it does neutralise the acid.
Q155MediumBPSC Prelims
The law of conservation of mass states:
AMass is always created in chemical reactions
BMass is always destroyed in chemical reactions
CMass is neither created nor destroyed in a chemical reaction
DMass changes proportionally with temperature
Show Answer
✔ C — Mass is neither created nor destroyed in a chemical reaction
Law of Conservation of Mass (Lavoisier, 1789): In a chemical reaction, the total mass of reactants equals the total mass of products.
Mass of reactants = Mass of products
Example: 2H₂ + O₂ → 2H₂O
4g + 32g → 36g ✓ (mass conserved)
This law holds for ordinary chemical reactions. (Note: In nuclear reactions, mass converts to energy per E = mc² — but this is not chemistry.)
*Why A is wrong:* Mass is never created — it's conserved.
*Why B is wrong:* Mass is never destroyed — it's conserved.
*Why D is wrong:* Temperature changes don't alter mass in chemical reactions.
Mass of reactants = Mass of products
Example: 2H₂ + O₂ → 2H₂O
4g + 32g → 36g ✓ (mass conserved)
This law holds for ordinary chemical reactions. (Note: In nuclear reactions, mass converts to energy per E = mc² — but this is not chemistry.)
*Why A is wrong:* Mass is never created — it's conserved.
*Why B is wrong:* Mass is never destroyed — it's conserved.
*Why D is wrong:* Temperature changes don't alter mass in chemical reactions.
Q156MediumBPSC Prelims
When excess zinc reacts with dilute sulphuric acid, which gas is produced?
AOxygen
BSulphur dioxide
CHydrogen
DCarbon dioxide
Show Answer
✔ C — Hydrogen
Zn + H₂SO₄ (dilute) → ZnSO₄ + H₂↑ (hydrogen gas)
Active metals above hydrogen in reactivity series react with dilute acids to produce hydrogen gas:
Mg, Al, Zn, Fe, Ni, Sn + dilute acid → salt + H₂↑
Hydrogen gas test: burns with a pop sound (lighted splint test)
*Why A is wrong:* Oxygen is not produced — it would require decomposition of water or a different reaction.
*Why B is wrong:* SO₂ (sulphur dioxide) is produced with CONCENTRATED H₂SO₄ (oxidising reaction) — NOT dilute.
*Why C is wrong:* Wait — C is the correct answer (hydrogen).
*Why D is wrong:* CO₂ is produced when acid reacts with carbonates (CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂).
Active metals above hydrogen in reactivity series react with dilute acids to produce hydrogen gas:
Mg, Al, Zn, Fe, Ni, Sn + dilute acid → salt + H₂↑
Hydrogen gas test: burns with a pop sound (lighted splint test)
*Why A is wrong:* Oxygen is not produced — it would require decomposition of water or a different reaction.
*Why B is wrong:* SO₂ (sulphur dioxide) is produced with CONCENTRATED H₂SO₄ (oxidising reaction) — NOT dilute.
*Why C is wrong:* Wait — C is the correct answer (hydrogen).
*Why D is wrong:* CO₂ is produced when acid reacts with carbonates (CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂).
Q157HardBPSC Prelims
In which of the following reactions does the oxidation state of nitrogen change?
ANaOH + HNO₃ → NaNO₃: N in HNO₃ = +5; N in NaNO₃ = +5. No change.
B3NO₂ + H₂O → 2HNO₃ + NO:
CNH₄Cl → NH₃ + HCl: N in NH₄⁺ = −3; N in NH₃ = −3. No change.
DCa(NO₃)₂ → CaO + 2NO₂ + ½O₂: N goes from +5 → +4 (reduction). This IS a change.
Show Answer
✔ B — 3NO₂ + H₂O → 2HNO₃ + NO:
Tracking nitrogen oxidation states:
A) NaOH + HNO₃ → NaNO₃: N in HNO₃ = +5; N in NaNO₃ = +5. No change.
B) 3NO₂ + H₂O → 2HNO₃ + NO:
- N in NO₂ = +4
- N in HNO₃ = +5 (oxidised from +4)
- N in NO = +2 (reduced from +4)
This is a disproportionation reaction — NO₂ simultaneously oxidises and reduces.
C) NH₄Cl → NH₃ + HCl: N in NH₄⁺ = −3; N in NH₃ = −3. No change.
D) Ca(NO₃)₂ → CaO + 2NO₂ + ½O₂: N goes from +5 → +4 (reduction). This IS a change.
Actually both B and D show nitrogen oxidation state change. But B is the "disproportionation" answer and is the best answer for BPSC purposes (D is thermal decomposition).
*Why A is wrong:* N stays at +5 throughout (acid-base neutralisation).
*Why C is wrong:* N stays at −3 (simple thermal decomposition).
A) NaOH + HNO₃ → NaNO₃: N in HNO₃ = +5; N in NaNO₃ = +5. No change.
B) 3NO₂ + H₂O → 2HNO₃ + NO:
- N in NO₂ = +4
- N in HNO₃ = +5 (oxidised from +4)
- N in NO = +2 (reduced from +4)
This is a disproportionation reaction — NO₂ simultaneously oxidises and reduces.
C) NH₄Cl → NH₃ + HCl: N in NH₄⁺ = −3; N in NH₃ = −3. No change.
D) Ca(NO₃)₂ → CaO + 2NO₂ + ½O₂: N goes from +5 → +4 (reduction). This IS a change.
Actually both B and D show nitrogen oxidation state change. But B is the "disproportionation" answer and is the best answer for BPSC purposes (D is thermal decomposition).
*Why A is wrong:* N stays at +5 throughout (acid-base neutralisation).
*Why C is wrong:* N stays at −3 (simple thermal decomposition).
Q158HardBPSC Prelims
The rate of a chemical reaction is generally increased by:
ADecreasing temperature
BDecreasing concentration of reactants
CAdding a catalyst
DRemoving a catalyst
Show Answer
✔ C — Adding a catalyst
Factors that increase reaction rate:
1. Temperature increase: more kinetic energy → more effective collisions
2. Concentration increase: more particles → more collisions
3. Catalyst: lowers activation energy → more reactions per second
4. Surface area increase: more exposed particles → more collisions
5. Pressure increase (for gases): effectively increases concentration
A catalyst increases reaction rate WITHOUT being consumed or changing the overall reaction energy.
*Why A is wrong:* Decreasing temperature SLOWS reaction rate (fewer collisions).
*Why B is wrong:* Decreasing concentration SLOWS reaction rate (fewer particles to collide).
*Why D is wrong:* Removing catalyst slows the reaction (no activation energy lowering).
1. Temperature increase: more kinetic energy → more effective collisions
2. Concentration increase: more particles → more collisions
3. Catalyst: lowers activation energy → more reactions per second
4. Surface area increase: more exposed particles → more collisions
5. Pressure increase (for gases): effectively increases concentration
A catalyst increases reaction rate WITHOUT being consumed or changing the overall reaction energy.
*Why A is wrong:* Decreasing temperature SLOWS reaction rate (fewer collisions).
*Why B is wrong:* Decreasing concentration SLOWS reaction rate (fewer particles to collide).
*Why D is wrong:* Removing catalyst slows the reaction (no activation energy lowering).
Q159HardBPSC Prelims
Le Chatelier's Principle states that if a system in equilibrium is disturbed, the system:
AShifts in the direction that increases the disturbance
BShifts in the direction that counteracts the disturbance to restore equilibrium
CRemains unaffected by any disturbance
DAlways shifts towards the products side
Show Answer
✔ B — Shifts in the direction that counteracts the disturbance to restore equilibrium
Le Chatelier's Principle (1884): When a system at equilibrium is subjected to a stress (change in concentration, temperature, or pressure), the system responds by shifting the equilibrium in the direction that partially counteracts the stress.
Applications:
- Increase [reactant] → equilibrium shifts toward products
- Increase temperature → shifts toward endothermic direction
- Increase pressure → shifts toward fewer moles of gas
Haber process (N₂ + 3H₂ ⇌ 2NH₃): high pressure shifts → products (fewer moles: 4 → 2); low temperature favours products but slow rate → compromise at 450°C.
*Why A is wrong:* System counteracts (opposes) the disturbance — it doesn't amplify it.
*Why C is wrong:* The equilibrium IS affected and shifts — it doesn't remain static.
*Why D is wrong:* Shifts can be toward reactants OR products depending on the disturbance.
Applications:
- Increase [reactant] → equilibrium shifts toward products
- Increase temperature → shifts toward endothermic direction
- Increase pressure → shifts toward fewer moles of gas
Haber process (N₂ + 3H₂ ⇌ 2NH₃): high pressure shifts → products (fewer moles: 4 → 2); low temperature favours products but slow rate → compromise at 450°C.
*Why A is wrong:* System counteracts (opposes) the disturbance — it doesn't amplify it.
*Why C is wrong:* The equilibrium IS affected and shifts — it doesn't remain static.
*Why D is wrong:* Shifts can be toward reactants OR products depending on the disturbance.
Q160HardBPSC Prelims
The decomposition of hydrogen peroxide (H₂O₂) is catalysed by MnO₂. In this reaction, MnO₂ is:
AConsumed in the reaction
BA reactant that is converted to MnO
CA catalyst — it is recovered unchanged at the end
DAn inhibitor that slows the reaction
Show Answer
✔ C — A catalyst — it is recovered unchanged at the end
2H₂O₂ → 2H₂O + O₂ (MnO₂ as catalyst)
MnO₂ (manganese dioxide) acts as a catalyst: it speeds up the reaction but is not consumed — the same amount of MnO₂ is present before and after the reaction.
Catalyst mechanism: MnO₂ lowers the activation energy by providing an alternative reaction pathway. It temporarily reacts with H₂O₂ to form an intermediate, then is regenerated.
*Why A is wrong:* Catalysts are not consumed — they are recovered unchanged.
*Why B is wrong:* MnO₂ is not converted to MnO — it remains as MnO₂.
*Why D is wrong:* An inhibitor slows reactions (negative catalyst). MnO₂ speeds it up.
MnO₂ (manganese dioxide) acts as a catalyst: it speeds up the reaction but is not consumed — the same amount of MnO₂ is present before and after the reaction.
Catalyst mechanism: MnO₂ lowers the activation energy by providing an alternative reaction pathway. It temporarily reacts with H₂O₂ to form an intermediate, then is regenerated.
*Why A is wrong:* Catalysts are not consumed — they are recovered unchanged.
*Why B is wrong:* MnO₂ is not converted to MnO — it remains as MnO₂.
*Why D is wrong:* An inhibitor slows reactions (negative catalyst). MnO₂ speeds it up.
Electrochemistry
Q161EasyBPSC Prelims
In an electrolytic cell, the electrode connected to the negative terminal of the battery is called:
AAnode
BCathode
CElectrode
DElectrolyte
Show Answer
✔ B — Cathode
Electrolytic cell (uses external electricity to drive non-spontaneous reactions):
- Cathode = negative electrode (connected to negative terminal)
- Cations (positive ions) move toward cathode
- Reduction occurs at cathode: M^n+ + ne⁻ → M
- Anode = positive electrode (connected to positive terminal)
- Anions (negative ions) move toward anode
- Oxidation occurs at anode: M → M^n+ + ne⁻
Memory aid: CAtHode = reduction (CAT = positively charged cations move to cathode)
*Why A is wrong:* Anode = positive terminal → oxidation occurs.
*Why C is wrong:* "Electrode" is a general term for either anode or cathode.
*Why D is wrong:* Electrolyte = the solution/molten substance that conducts electricity (not an electrode).
- Cathode = negative electrode (connected to negative terminal)
- Cations (positive ions) move toward cathode
- Reduction occurs at cathode: M^n+ + ne⁻ → M
- Anode = positive electrode (connected to positive terminal)
- Anions (negative ions) move toward anode
- Oxidation occurs at anode: M → M^n+ + ne⁻
Memory aid: CAtHode = reduction (CAT = positively charged cations move to cathode)
*Why A is wrong:* Anode = positive terminal → oxidation occurs.
*Why C is wrong:* "Electrode" is a general term for either anode or cathode.
*Why D is wrong:* Electrolyte = the solution/molten substance that conducts electricity (not an electrode).
Q162EasyBPSC Prelims
A galvanic (voltaic) cell converts:
AElectrical energy into chemical energy
BChemical energy into electrical energy
CHeat energy into electrical energy
DMechanical energy into chemical energy
Show Answer
✔ B — Chemical energy into electrical energy
Galvanic/Voltaic cell: converts chemical energy → electrical energy (spontaneous redox reaction drives current)
Example: Daniell cell (Zn-Cu): Zn|ZnSO₄||CuSO₄|Cu (EMF = 1.1V)
Electrolytic cell: converts electrical energy → chemical energy (external electricity drives non-spontaneous reaction)
Comparison:
- Battery (galvanic): chemical → electrical
- Charging a battery (electrolytic): electrical → chemical
- Thermocouple: heat → electrical
- Generator: mechanical → electrical
*Why A is wrong:* Electrical → chemical = electrolytic cell (charging process).
*Why C is wrong:* Heat → electrical = thermoelectric/Seebeck effect (thermocouple).
*Why D is wrong:* Mechanical → chemical is not a standard energy conversion in chemistry.
Example: Daniell cell (Zn-Cu): Zn|ZnSO₄||CuSO₄|Cu (EMF = 1.1V)
Electrolytic cell: converts electrical energy → chemical energy (external electricity drives non-spontaneous reaction)
Comparison:
- Battery (galvanic): chemical → electrical
- Charging a battery (electrolytic): electrical → chemical
- Thermocouple: heat → electrical
- Generator: mechanical → electrical
*Why A is wrong:* Electrical → chemical = electrolytic cell (charging process).
*Why C is wrong:* Heat → electrical = thermoelectric/Seebeck effect (thermocouple).
*Why D is wrong:* Mechanical → chemical is not a standard energy conversion in chemistry.
Q163MediumBPSC Prelims
In the electrolysis of dilute sulphuric acid (H₂SO₄), what is produced at the anode?
AHydrogen gas
BSulphur gas
COxygen gas
DSulphur dioxide gas
Show Answer
✔ C — Oxygen gas
Electrolysis of dilute H₂SO₄:
- Anode (+): water is oxidised: 2H₂O → O₂ + 4H⁺ + 4e⁻ → Oxygen gas produced
- Cathode (−): H⁺ is reduced: 4H⁺ + 4e⁻ → 2H₂ → Hydrogen gas produced
Overall: 2H₂O → 2H₂ + O₂ (electrolysis of water — acid just provides conductivity)
Volume ratio: H₂ : O₂ = 2 : 1 (by volume)
*Why A is wrong:* Hydrogen is produced at the CATHODE — not the anode.
*Why B is wrong:* Sulphur gas is not produced; SO₄²⁻ ions are not discharged preferentially at the anode.
*Why D is wrong:* SO₂ would only form at high concentration with special conditions — not in dilute H₂SO₄ electrolysis.
- Anode (+): water is oxidised: 2H₂O → O₂ + 4H⁺ + 4e⁻ → Oxygen gas produced
- Cathode (−): H⁺ is reduced: 4H⁺ + 4e⁻ → 2H₂ → Hydrogen gas produced
Overall: 2H₂O → 2H₂ + O₂ (electrolysis of water — acid just provides conductivity)
Volume ratio: H₂ : O₂ = 2 : 1 (by volume)
*Why A is wrong:* Hydrogen is produced at the CATHODE — not the anode.
*Why B is wrong:* Sulphur gas is not produced; SO₄²⁻ ions are not discharged preferentially at the anode.
*Why D is wrong:* SO₂ would only form at high concentration with special conditions — not in dilute H₂SO₄ electrolysis.
Q164MediumBPSC Prelims
The standard hydrogen electrode (SHE) has an electrode potential of:
A−1.0 V
B+1.0 V
C0.00 V (by definition)
D+0.5 V
Show Answer
✔ C — 0.00 V (by definition)
The Standard Hydrogen Electrode (SHE) is the reference electrode with potential defined as exactly 0.00 V (by international convention).
- H₂(g, 1 atm) | H⁺(aq, 1 M) | Pt
- 2H⁺ + 2e⁻ ⇌ H₂ (E° = 0.00 V)
All other electrode potentials are measured relative to the SHE. For example:
- Zn²⁺/Zn: E° = −0.76 V (below SHE → more easily oxidised)
- Cu²⁺/Cu: E° = +0.34 V (above SHE → more easily reduced)
- F₂/F⁻: E° = +2.87 V (strongest oxidising agent)
*Why A is wrong:* −1.0 V is not the defined SHE potential.
*Why B is wrong:* +1.0 V is not the SHE potential.
*Why D is wrong:* +0.5 V is not the SHE potential.
- H₂(g, 1 atm) | H⁺(aq, 1 M) | Pt
- 2H⁺ + 2e⁻ ⇌ H₂ (E° = 0.00 V)
All other electrode potentials are measured relative to the SHE. For example:
- Zn²⁺/Zn: E° = −0.76 V (below SHE → more easily oxidised)
- Cu²⁺/Cu: E° = +0.34 V (above SHE → more easily reduced)
- F₂/F⁻: E° = +2.87 V (strongest oxidising agent)
*Why A is wrong:* −1.0 V is not the defined SHE potential.
*Why B is wrong:* +1.0 V is not the SHE potential.
*Why D is wrong:* +0.5 V is not the SHE potential.
Q165HardBPSC Prelims
Electroplating of an object with gold involves:
AMaking the object the anode and using gold solution as electrolyte
BMaking the object the cathode and using gold salt solution as electrolyte
CDipping the object in molten gold
DCoating the object with gold paint under vacuum
Show Answer
✔ B — Making the object the cathode and using gold salt solution as electrolyte
Electroplating process (gold on jewellery):
- Object to be plated = CATHODE (negative) — gold ions deposit on it
- Pure gold bar = ANODE (positive) — dissolves to replenish gold ions
- Electrolyte = gold salt solution (gold chloride AuCl₃ or potassium gold cyanide K[Au(CN)₂])
At cathode: Au³⁺ + 3e⁻ → Au (gold deposits on object)
At anode: Au → Au³⁺ + 3e⁻ (gold dissolves into solution)
*Why A is wrong:* Anode = the gold metal that dissolves; the object is the CATHODE.
*Why C is wrong:* Dipping in molten gold = physical process, not electroplating — would require extremely high temperature (1064°C melting point of gold).
*Why D is wrong:* Vacuum coating is Physical Vapour Deposition (PVD) — a different process, not electroplating.
- Object to be plated = CATHODE (negative) — gold ions deposit on it
- Pure gold bar = ANODE (positive) — dissolves to replenish gold ions
- Electrolyte = gold salt solution (gold chloride AuCl₃ or potassium gold cyanide K[Au(CN)₂])
At cathode: Au³⁺ + 3e⁻ → Au (gold deposits on object)
At anode: Au → Au³⁺ + 3e⁻ (gold dissolves into solution)
*Why A is wrong:* Anode = the gold metal that dissolves; the object is the CATHODE.
*Why C is wrong:* Dipping in molten gold = physical process, not electroplating — would require extremely high temperature (1064°C melting point of gold).
*Why D is wrong:* Vacuum coating is Physical Vapour Deposition (PVD) — a different process, not electroplating.
Q166HardBPSC Prelims
A lead-acid battery (used in cars) consists of:
ALead anode, lead cathode, and sulphuric acid electrolyte
BZinc anode, copper cathode, and ZnSO₄ electrolyte
CLead anode, lead dioxide cathode, and sulphuric acid electrolyte
DCarbon anode, zinc cathode, and ammonium chloride electrolyte
Show Answer
✔ C — Lead anode, lead dioxide cathode, and sulphuric acid electrolyte
Lead-acid battery (secondary/rechargeable cell):
- Anode (negative plate): Lead (Pb)
- Cathode (positive plate): Lead dioxide (PbO₂)
- Electrolyte: dilute sulphuric acid (H₂SO₄, ~37% solution, density 1.28 g/mL)
Discharging:
- Anode: Pb + SO₄²⁻ → PbSO₄ + 2e⁻ (Pb oxidised)
- Cathode: PbO₂ + SO₄²⁻ + 4H⁺ + 2e⁻ → PbSO₄ + 2H₂O (PbO₂ reduced)
- Both electrodes → PbSO₄ on discharge (battery "dead" when both become PbSO₄)
Recharging reverses the reactions.
*Why A is wrong:* Both anode AND cathode being lead is wrong — cathode is PbO₂ (lead dioxide).
*Why B is wrong:* Zn/Cu/ZnSO₄ = Daniell cell — NOT a lead-acid battery.
*Why D is wrong:* C/Zn/NH₄Cl = Leclanché/dry cell (ordinary batteries).
- Anode (negative plate): Lead (Pb)
- Cathode (positive plate): Lead dioxide (PbO₂)
- Electrolyte: dilute sulphuric acid (H₂SO₄, ~37% solution, density 1.28 g/mL)
Discharging:
- Anode: Pb + SO₄²⁻ → PbSO₄ + 2e⁻ (Pb oxidised)
- Cathode: PbO₂ + SO₄²⁻ + 4H⁺ + 2e⁻ → PbSO₄ + 2H₂O (PbO₂ reduced)
- Both electrodes → PbSO₄ on discharge (battery "dead" when both become PbSO₄)
Recharging reverses the reactions.
*Why A is wrong:* Both anode AND cathode being lead is wrong — cathode is PbO₂ (lead dioxide).
*Why B is wrong:* Zn/Cu/ZnSO₄ = Daniell cell — NOT a lead-acid battery.
*Why D is wrong:* C/Zn/NH₄Cl = Leclanché/dry cell (ordinary batteries).
Q167HardBPSC Prelims
Faraday's First Law of Electrolysis states:
AThe mass of substance deposited is proportional to the atomic mass of the element
BThe mass of substance deposited at an electrode is directly proportional to the quantity of charge passed
CElectrode potential is proportional to temperature
DCurrent is inversely proportional to resistance
Show Answer
✔ B — The mass of substance deposited at an electrode is directly proportional to the quantity of charge passed
Faraday's First Law of Electrolysis: m = ZQ = ZIt
Where:
- m = mass deposited (grams)
- Z = electrochemical equivalent (g/coulomb)
- Q = charge (coulombs) = I × t (current × time)
- I = current (amperes); t = time (seconds)
Mass deposited is directly proportional to:
- Current (more current → more ions discharged)
- Time (more time → more charge passed)
Faraday's Second Law: Mass ∝ (Molar mass / Valency) — same charge deposits different masses of different elements.
*Why A is wrong:* Atomic mass is part of the equivalents (Second Law), not First Law.
*Why C is wrong:* Electrode potential and temperature — Nernst equation, not Faraday's Law.
*Why D is wrong:* Ohm's Law (V = IR) — unrelated to electrolysis.
Where:
- m = mass deposited (grams)
- Z = electrochemical equivalent (g/coulomb)
- Q = charge (coulombs) = I × t (current × time)
- I = current (amperes); t = time (seconds)
Mass deposited is directly proportional to:
- Current (more current → more ions discharged)
- Time (more time → more charge passed)
Faraday's Second Law: Mass ∝ (Molar mass / Valency) — same charge deposits different masses of different elements.
*Why A is wrong:* Atomic mass is part of the equivalents (Second Law), not First Law.
*Why C is wrong:* Electrode potential and temperature — Nernst equation, not Faraday's Law.
*Why D is wrong:* Ohm's Law (V = IR) — unrelated to electrolysis.
Q168MediumBPSC Prelims
Corrosion of iron (rusting) is an electrochemical process. Which of the following best explains why iron rusts faster in salt water than pure water?
ASalt water contains more oxygen
BSalt water is more acidic than pure water
CSalt water has higher electrical conductivity, facilitating faster electrochemical corrosion
DSalt water has lower pH, which dissolves iron faster
Show Answer
✔ C — Salt water has higher electrical conductivity, facilitating faster electrochemical corrosion
Rusting = electrochemical corrosion requiring water and oxygen. The iron surface has micro-anodic and micro-cathodic regions:
- Anodic: Fe → Fe²⁺ + 2e⁻ (iron dissolves)
- Cathodic: O₂ + 4H⁺ + 4e⁻ → 2H₂O
Salt water (NaCl solution) has much higher electrical conductivity (Na⁺ and Cl⁻ ions carry current) → electrons flow faster between anodic and cathodic sites → faster rusting.
Additionally, Cl⁻ ions penetrate the passive oxide film on iron, accelerating corrosion.
*Why A is wrong:* Dissolved O₂ is actually LOWER in salt water than pure water (salting out effect).
*Why B is wrong:* NaCl solution is approximately neutral (pH ~7) — not significantly more acidic.
*Why D is wrong:* pH of salt water is neutral — it doesn't dissolve iron significantly by itself.
- Anodic: Fe → Fe²⁺ + 2e⁻ (iron dissolves)
- Cathodic: O₂ + 4H⁺ + 4e⁻ → 2H₂O
Salt water (NaCl solution) has much higher electrical conductivity (Na⁺ and Cl⁻ ions carry current) → electrons flow faster between anodic and cathodic sites → faster rusting.
Additionally, Cl⁻ ions penetrate the passive oxide film on iron, accelerating corrosion.
*Why A is wrong:* Dissolved O₂ is actually LOWER in salt water than pure water (salting out effect).
*Why B is wrong:* NaCl solution is approximately neutral (pH ~7) — not significantly more acidic.
*Why D is wrong:* pH of salt water is neutral — it doesn't dissolve iron significantly by itself.
Q169MediumBPSC Prelims
The dry cell (Leclanché cell) used in torches has which components?
AZinc cathode, copper anode, ZnSO₄ electrolyte
BCarbon rod anode (positive), zinc casing cathode (negative), ammonium chloride paste electrolyte
CLead anode, lead dioxide cathode, dilute H₂SO₄
DLithium anode, CoO₂ cathode, organic electrolyte
Show Answer
✔ B — Carbon rod anode (positive), zinc casing cathode (negative), ammonium chloride paste electrolyte
Dry cell (Leclanché cell): portable primary battery (non-rechargeable)
- Cathode (negative, outer): Zinc casing (Zn → Zn²⁺ + 2e⁻)
- Anode (positive, central): Carbon (graphite) rod surrounded by MnO₂
- Electrolyte: paste of NH₄Cl + ZnCl₂ + sawdust/flour
Reactions:
- Zn (cathode): Zn → Zn²⁺ + 2e⁻ (zinc is oxidised — zinc is the negative terminal)
- MnO₂/C (anode): 2MnO₂ + 2NH₄⁺ + 2e⁻ → Mn₂O₃ + 2NH₃ + H₂O (reduction occurs)
EMF ≈ 1.5 V
*Why A is wrong:* Zinc is the NEGATIVE electrode (cathode in this context — the electrode where oxidation occurs = conventionally anode); carbon is the positive rod (common confusion with naming).
*Why C is wrong:* Lead/PbO₂/H₂SO₄ = lead-acid battery.
*Why D is wrong:* Li/CoO₂/organic = lithium-ion battery (modern rechargeable).
- Cathode (negative, outer): Zinc casing (Zn → Zn²⁺ + 2e⁻)
- Anode (positive, central): Carbon (graphite) rod surrounded by MnO₂
- Electrolyte: paste of NH₄Cl + ZnCl₂ + sawdust/flour
Reactions:
- Zn (cathode): Zn → Zn²⁺ + 2e⁻ (zinc is oxidised — zinc is the negative terminal)
- MnO₂/C (anode): 2MnO₂ + 2NH₄⁺ + 2e⁻ → Mn₂O₃ + 2NH₃ + H₂O (reduction occurs)
EMF ≈ 1.5 V
*Why A is wrong:* Zinc is the NEGATIVE electrode (cathode in this context — the electrode where oxidation occurs = conventionally anode); carbon is the positive rod (common confusion with naming).
*Why C is wrong:* Lead/PbO₂/H₂SO₄ = lead-acid battery.
*Why D is wrong:* Li/CoO₂/organic = lithium-ion battery (modern rechargeable).
Q170HardBPSC Prelims
The EMF (electromotive force) of a cell is measured in:
AAmperes
BOhms
CVolts
DWatts
Show Answer
✔ C — Volts
EMF (Electromotive Force): the potential difference between the two electrodes of a cell when no current flows. Measured in Volts (V).
EMF = Reduction potential of cathode − Reduction potential of anode
For Daniell cell: E°cell = E°Cu²⁺/Cu − E°Zn²⁺/Zn = 0.34 − (−0.76) = 1.10 V
Units:
- EMF/Potential: Volts (V)
- Current: Amperes (A)
- Resistance: Ohms (Ω)
- Power: Watts (W) = V × A
*Why A is wrong:* Amperes = current (flow of charge per second).
*Why B is wrong:* Ohms = resistance (opposition to current flow).
*Why D is wrong:* Watts = power (rate of energy transfer = V × A).
EMF = Reduction potential of cathode − Reduction potential of anode
For Daniell cell: E°cell = E°Cu²⁺/Cu − E°Zn²⁺/Zn = 0.34 − (−0.76) = 1.10 V
Units:
- EMF/Potential: Volts (V)
- Current: Amperes (A)
- Resistance: Ohms (Ω)
- Power: Watts (W) = V × A
*Why A is wrong:* Amperes = current (flow of charge per second).
*Why B is wrong:* Ohms = resistance (opposition to current flow).
*Why D is wrong:* Watts = power (rate of energy transfer = V × A).
Important Chemical Compounds
Q171EasyBPSC Prelims
Common salt (table salt) is chemically:
ANaHCO₃ (Sodium bicarbonate)
BNaCl (Sodium chloride)
CNa₂CO₃ (Sodium carbonate)
DNaOH (Sodium hydroxide)
Show Answer
✔ B — NaCl (Sodium chloride)
Common salt = NaCl (Sodium chloride)
- Ionic compound: Na⁺ and Cl⁻
- Found in sea water (~3.5% NaCl), rock salt deposits (halite), and underground brine
- Essential for human health (nerve function, fluid balance, gastric HCl production)
*Why A is wrong:* NaHCO₃ = baking soda (used in cooking, antacid).
*Why C is wrong:* Na₂CO₃ = washing soda (used in cleaning, glass making).
*Why D is wrong:* NaOH = caustic soda (used in soap making, drain cleaners).
- Ionic compound: Na⁺ and Cl⁻
- Found in sea water (~3.5% NaCl), rock salt deposits (halite), and underground brine
- Essential for human health (nerve function, fluid balance, gastric HCl production)
*Why A is wrong:* NaHCO₃ = baking soda (used in cooking, antacid).
*Why C is wrong:* Na₂CO₃ = washing soda (used in cleaning, glass making).
*Why D is wrong:* NaOH = caustic soda (used in soap making, drain cleaners).
Q172EasyBPSC Prelims
"Heavy water" used in nuclear reactors is:
AWater with dissolved minerals (hard water)
BWater with higher pressure
CWater where hydrogen is replaced by deuterium (D₂O)
DIce water below 4°C
Show Answer
✔ C — Water where hydrogen is replaced by deuterium (D₂O)
Heavy water (D₂O): water in which ordinary hydrogen (¹H, protium) is replaced by deuterium (²H, D — an isotope with 1 neutron).
- Chemical formula: D₂O or ²H₂O
- Density: 1.11 g/mL (heavier than normal water, 1.00 g/mL)
- Melting point: 3.82°C (slightly higher than normal water)
Use in nuclear reactors: Moderator — slows down fast neutrons to thermal neutrons without absorbing them (unlike ordinary water), enabling sustained nuclear fission chain reaction.
India's CANDU-type reactors (Rajasthan Atomic Power Station) use heavy water as both moderator and coolant.
*Why A is wrong:* Hard water = contains dissolved Ca²⁺/Mg²⁺ salts — not "heavy water."
*Why B is wrong:* Water pressure doesn't create "heavy water."
*Why D is wrong:* Water below 4°C is just cold/ice — not heavy water.
- Chemical formula: D₂O or ²H₂O
- Density: 1.11 g/mL (heavier than normal water, 1.00 g/mL)
- Melting point: 3.82°C (slightly higher than normal water)
Use in nuclear reactors: Moderator — slows down fast neutrons to thermal neutrons without absorbing them (unlike ordinary water), enabling sustained nuclear fission chain reaction.
India's CANDU-type reactors (Rajasthan Atomic Power Station) use heavy water as both moderator and coolant.
*Why A is wrong:* Hard water = contains dissolved Ca²⁺/Mg²⁺ salts — not "heavy water."
*Why B is wrong:* Water pressure doesn't create "heavy water."
*Why D is wrong:* Water below 4°C is just cold/ice — not heavy water.
Q173MediumBPSC Prelims
Aspirin is the common name for which chemical compound?
AParacetamol (acetaminophen)
BAcetylsalicylic acid
CIbuprofen
DAmoxicillin
Show Answer
✔ B — Acetylsalicylic acid
Aspirin = Acetylsalicylic acid (CH₃COO-C₆H₄-COOH)
- Synthesised by acetylation of salicylic acid with acetic anhydride
- Properties: analgesic (pain reliever), antipyretic (fever reducer), anti-inflammatory, anticoagulant (blood thinner)
- Discovered by Felix Hoffmann at Bayer (1897)
- First commercial NSAID (Non-Steroidal Anti-Inflammatory Drug)
- Low-dose aspirin (75-100 mg) used for cardiovascular protection
*Why A is wrong:* Paracetamol (acetaminophen) = N-acetyl-p-aminophenol — different drug, for pain/fever.
*Why C is wrong:* Ibuprofen = another NSAID, derived from propionic acid — different structure.
*Why D is wrong:* Amoxicillin = beta-lactam antibiotic — completely different class of drugs.
- Synthesised by acetylation of salicylic acid with acetic anhydride
- Properties: analgesic (pain reliever), antipyretic (fever reducer), anti-inflammatory, anticoagulant (blood thinner)
- Discovered by Felix Hoffmann at Bayer (1897)
- First commercial NSAID (Non-Steroidal Anti-Inflammatory Drug)
- Low-dose aspirin (75-100 mg) used for cardiovascular protection
*Why A is wrong:* Paracetamol (acetaminophen) = N-acetyl-p-aminophenol — different drug, for pain/fever.
*Why C is wrong:* Ibuprofen = another NSAID, derived from propionic acid — different structure.
*Why D is wrong:* Amoxicillin = beta-lactam antibiotic — completely different class of drugs.
Q174MediumBPSC Prelims
Chloroform (trichloromethane, CHCl₃) was historically used as:
AA fertilizer in agriculture
BAn anaesthetic in surgery
CA food preservative
DA fuel for automobiles
Show Answer
✔ B — An anaesthetic in surgery
Chloroform (CHCl₃): historically used as a general anaesthetic (1847 onwards) — James Young Simpson used it to induce unconsciousness during surgery and childbirth.
Properties that made it useful as anaesthetic:
- Heavier vapour (density 1.48 g/mL) → slow evaporation
- Sweet smell
- Quick unconsciousness when inhaled
Replaced by: safer anaesthetics (halothane, isoflurane) due to chloroform's toxicity and hepatotoxicity.
Modern uses of chloroform: solvent for fats, alkaloids, and resins; production of Freon refrigerants.
*Why A is wrong:* Chloroform is toxic — never used as a fertilizer.
*Why C is wrong:* Chloroform is toxic to consume — not a food preservative (preservatives: vinegar, salt, sugar, benzoic acid, sorbic acid).
*Why D is wrong:* Chloroform is not a fuel — it's a chlorinated solvent.
Properties that made it useful as anaesthetic:
- Heavier vapour (density 1.48 g/mL) → slow evaporation
- Sweet smell
- Quick unconsciousness when inhaled
Replaced by: safer anaesthetics (halothane, isoflurane) due to chloroform's toxicity and hepatotoxicity.
Modern uses of chloroform: solvent for fats, alkaloids, and resins; production of Freon refrigerants.
*Why A is wrong:* Chloroform is toxic — never used as a fertilizer.
*Why C is wrong:* Chloroform is toxic to consume — not a food preservative (preservatives: vinegar, salt, sugar, benzoic acid, sorbic acid).
*Why D is wrong:* Chloroform is not a fuel — it's a chlorinated solvent.
Q175MediumBPSC Prelims
DDT (Dichloro-Diphenyl-Trichloroethane) was widely used as:
AA fertilizer to increase crop yield
BA pesticide (insecticide) — now banned due to environmental persistence
CA preservative in food processing
DA fuel additive to increase octane rating
Show Answer
✔ B — A pesticide (insecticide) — now banned due to environmental persistence
DDT: Organochlorine insecticide developed in the 1940s.
- Effective against mosquitoes (malaria), lice (typhus), and agricultural pests
- Paul Müller received Nobel Prize (1948) for discovering insecticidal properties
- Used widely during World War II and post-war era
Why banned:
- Persistent Organic Pollutant (POP) — doesn't break down in environment
- Bioaccumulation and biomagnification in food chains (especially in birds — eagle eggshell thinning)
- Potential human carcinogen
- Rachel Carson's "Silent Spring" (1962) highlighted its ecological damage
- Stockholm Convention (2001) banned DDT globally (except limited malaria control use)
- India phased out agricultural use; still used in limited quantity for indoor residual spraying (IRS) for malaria in tribal areas
*Why A is wrong:* DDT is toxic — not a fertilizer.
*Why C is wrong:* DDT is toxic for consumption — not a food preservative.
*Why D is wrong:* DDT is not a fuel additive.
- Effective against mosquitoes (malaria), lice (typhus), and agricultural pests
- Paul Müller received Nobel Prize (1948) for discovering insecticidal properties
- Used widely during World War II and post-war era
Why banned:
- Persistent Organic Pollutant (POP) — doesn't break down in environment
- Bioaccumulation and biomagnification in food chains (especially in birds — eagle eggshell thinning)
- Potential human carcinogen
- Rachel Carson's "Silent Spring" (1962) highlighted its ecological damage
- Stockholm Convention (2001) banned DDT globally (except limited malaria control use)
- India phased out agricultural use; still used in limited quantity for indoor residual spraying (IRS) for malaria in tribal areas
*Why A is wrong:* DDT is toxic — not a fertilizer.
*Why C is wrong:* DDT is toxic for consumption — not a food preservative.
*Why D is wrong:* DDT is not a fuel additive.
Q176HardBPSC Prelims
Nitrogen fixation refers to:
AConverting atmospheric N₂ into ammonia or nitrates usable by plants
BAdding nitrogen fertilizers directly to soil
CBurning nitrogen in factories
DRemoving nitrogen from the atmosphere to prevent acid rain
Show Answer
✔ A — Converting atmospheric N₂ into ammonia or nitrates usable by plants
Nitrogen fixation: conversion of atmospheric N₂ (inert dinitrogen gas) into nitrogen compounds (NH₃, NO₃⁻) that organisms can use.
Methods:
1. Biological fixation: Rhizobium bacteria (in legume root nodules), Azobacter (free-living); converts N₂ → NH₃ using nitrogenase enzyme. Accounts for ~100 million tonnes N/year globally.
2. Industrial (Haber process): N₂ + 3H₂ → 2NH₃ (Fe catalyst, 450°C, 200 atm)
3. Lightning (atmospheric): N₂ + O₂ → 2NO → HNO₃ (minor contribution)
*Why B is wrong:* Adding fertilizers is applying already-fixed nitrogen — not the process of fixation itself.
*Why C is wrong:* Burning nitrogen doesn't occur in practical contexts.
*Why D is wrong:* N₂ doesn't cause acid rain (SO₂ and NOₓ from combustion do) — removing atmospheric N₂ isn't nitrogen fixation.
Methods:
1. Biological fixation: Rhizobium bacteria (in legume root nodules), Azobacter (free-living); converts N₂ → NH₃ using nitrogenase enzyme. Accounts for ~100 million tonnes N/year globally.
2. Industrial (Haber process): N₂ + 3H₂ → 2NH₃ (Fe catalyst, 450°C, 200 atm)
3. Lightning (atmospheric): N₂ + O₂ → 2NO → HNO₃ (minor contribution)
*Why B is wrong:* Adding fertilizers is applying already-fixed nitrogen — not the process of fixation itself.
*Why C is wrong:* Burning nitrogen doesn't occur in practical contexts.
*Why D is wrong:* N₂ doesn't cause acid rain (SO₂ and NOₓ from combustion do) — removing atmospheric N₂ isn't nitrogen fixation.
Q177HardBPSC Prelims
Which of the following is NOT a greenhouse gas?
ACarbon dioxide (CO₂)
BMethane (CH₄)
CNitrous oxide (N₂O)
DNitrogen gas (N₂)
Show Answer
✔ D — Nitrogen gas (N₂)
Greenhouse gases: absorb and re-emit infrared radiation, trapping heat in the Earth's atmosphere.
Main greenhouse gases:
- CO₂ (carbon dioxide): 72% of GHG contribution from human activities
- CH₄ (methane): 25× more potent than CO₂ (over 100 years); rice paddies, cattle, landfills
- N₂O (nitrous oxide): 298× more potent than CO₂; from fertilizers, animal waste
- Water vapour (H₂O): most abundant GHG (natural)
- CFCs (chlorofluorocarbons): also potent GHGs and ozone destroyers
Nitrogen gas (N₂): makes up 78% of air but does NOT absorb infrared radiation → NOT a greenhouse gas. (Its molecule has no dipole moment change in vibration.)
*Why A is wrong:* CO₂ = major greenhouse gas.
*Why B is wrong:* CH₄ = potent greenhouse gas (BPSC 2023 tested this directly).
*Why C is wrong:* N₂O = nitrous oxide, potent GHG from agricultural sources.
Main greenhouse gases:
- CO₂ (carbon dioxide): 72% of GHG contribution from human activities
- CH₄ (methane): 25× more potent than CO₂ (over 100 years); rice paddies, cattle, landfills
- N₂O (nitrous oxide): 298× more potent than CO₂; from fertilizers, animal waste
- Water vapour (H₂O): most abundant GHG (natural)
- CFCs (chlorofluorocarbons): also potent GHGs and ozone destroyers
Nitrogen gas (N₂): makes up 78% of air but does NOT absorb infrared radiation → NOT a greenhouse gas. (Its molecule has no dipole moment change in vibration.)
*Why A is wrong:* CO₂ = major greenhouse gas.
*Why B is wrong:* CH₄ = potent greenhouse gas (BPSC 2023 tested this directly).
*Why C is wrong:* N₂O = nitrous oxide, potent GHG from agricultural sources.
Q178HardBPSC Prelims
What is "laughing gas" and what is its chemical formula?
ANitrogen gas (N₂) — people laugh when deprived of nitrogen
BNitrous oxide (N₂O) — causes euphoria and laughing when inhaled
CNitric oxide (NO) — combines with haemoglobin causing euphoria
DNitrogen dioxide (NO₂) — toxic but causes mild euphoria
Show Answer
✔ B — Nitrous oxide (N₂O) — causes euphoria and laughing when inhaled
"Laughing gas" = Nitrous oxide (N₂O)
- Colourless, sweet-smelling gas
- When inhaled: causes feelings of euphoria, light-headedness, and giggling → "laughing gas"
- Medical use: dental anaesthesia, surgical anaesthesia (especially paediatric)
- Also used as: oxidiser in rocket propellants, aerosol propellant in whipped cream cans
- GHG: 298× more potent than CO₂ for global warming
Properties: non-flammable, mildly sweet odour, decomposes at high temp: 2N₂O → 2N₂ + O₂ (this releases O₂ → helps combustion)
*Why A is wrong:* N₂ (dinitrogen) is inert and not "laughing gas."
*Why C is wrong:* NO (nitric oxide) is toxic/a signalling molecule — not laughing gas. (NO binds haemoglobin to cause vasodilation — basis of nitroglycerin for angina.)
*Why D is wrong:* NO₂ (nitrogen dioxide) is toxic (reddish-brown, pungent) — definitely not laughing gas.
- Colourless, sweet-smelling gas
- When inhaled: causes feelings of euphoria, light-headedness, and giggling → "laughing gas"
- Medical use: dental anaesthesia, surgical anaesthesia (especially paediatric)
- Also used as: oxidiser in rocket propellants, aerosol propellant in whipped cream cans
- GHG: 298× more potent than CO₂ for global warming
Properties: non-flammable, mildly sweet odour, decomposes at high temp: 2N₂O → 2N₂ + O₂ (this releases O₂ → helps combustion)
*Why A is wrong:* N₂ (dinitrogen) is inert and not "laughing gas."
*Why C is wrong:* NO (nitric oxide) is toxic/a signalling molecule — not laughing gas. (NO binds haemoglobin to cause vasodilation — basis of nitroglycerin for angina.)
*Why D is wrong:* NO₂ (nitrogen dioxide) is toxic (reddish-brown, pungent) — definitely not laughing gas.
Q179MediumBPSC Prelims
Milk of magnesia is used as an antacid. Its chemical composition is:
AMgSO₄ (Magnesium sulphate)
BMg(OH)₂ (Magnesium hydroxide)
CMgCl₂ (Magnesium chloride)
DMgCO₃ (Magnesium carbonate)
Show Answer
✔ B — Mg(OH)₂ (Magnesium hydroxide)
Milk of magnesia = Mg(OH)₂ (Magnesium hydroxide) — a white suspension in water
- Mechanism as antacid: Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O (neutralises excess stomach acid)
- Also used as laxative (draws water into intestines by osmosis)
- "Milk" appearance = white suspension (Mg(OH)₂ is slightly soluble)
Other Mg compounds:
- MgSO₄ = Epsom salt (laxative, magnesium supplement, sports bath)
- MgCl₂ = food additive (tofu coagulant), de-icing
- MgCO₃ = basic magnesium carbonate (in chalk/talcum powder)
*Why A is wrong:* MgSO₄ (Epsom salt) = different compound, different use.
*Why C is wrong:* MgCl₂ = magnesium chloride — not an antacid.
*Why D is wrong:* MgCO₃ reacts with HCl to give CO₂ (like baking soda) — not the primary component of milk of magnesia.
- Mechanism as antacid: Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O (neutralises excess stomach acid)
- Also used as laxative (draws water into intestines by osmosis)
- "Milk" appearance = white suspension (Mg(OH)₂ is slightly soluble)
Other Mg compounds:
- MgSO₄ = Epsom salt (laxative, magnesium supplement, sports bath)
- MgCl₂ = food additive (tofu coagulant), de-icing
- MgCO₃ = basic magnesium carbonate (in chalk/talcum powder)
*Why A is wrong:* MgSO₄ (Epsom salt) = different compound, different use.
*Why C is wrong:* MgCl₂ = magnesium chloride — not an antacid.
*Why D is wrong:* MgCO₃ reacts with HCl to give CO₂ (like baking soda) — not the primary component of milk of magnesia.
Q180HardBPSC Prelims
Carbon monoxide (CO) is a toxic gas. Its toxicity arises because:
AIt reacts with water to form carbonic acid, lowering blood pH
BIt binds to haemoglobin ~200 times more strongly than oxygen, preventing O₂ transport
CIt decomposes to carbon and oxygen in the lungs
DIt reacts with stomach acid to produce hydrogen cyanide
Show Answer
✔ B — It binds to haemoglobin ~200 times more strongly than oxygen, preventing O₂ transport
CO toxicity mechanism: Carbon monoxide binds to haemoglobin (Hb) forming carboxyhaemoglobin (COHb) with ~200-240 times greater affinity than oxygen:
- CO + Hb → COHb (very stable, blocks O₂ binding)
- Tissues receive insufficient O₂ → cellular hypoxia → death
CO poisoning symptoms: headache, dizziness, cherry-red skin (COHb is bright red), unconsciousness, death.
Treatment: 100% O₂ (displaces CO from Hb); hyperbaric O₂ for severe cases.
CO is colourless and odourless — "silent killer" (unlike LPG which has odorant added).
*Why A is wrong:* CO doesn't react with water at physiological pH — CO₂ does (forming H₂CO₃).
*Why C is wrong:* CO is stable in the lungs — it doesn't decompose.
*Why D is wrong:* CO doesn't produce hydrogen cyanide — cyanide poisoning has a different mechanism (binds cytochrome oxidase).
- CO + Hb → COHb (very stable, blocks O₂ binding)
- Tissues receive insufficient O₂ → cellular hypoxia → death
CO poisoning symptoms: headache, dizziness, cherry-red skin (COHb is bright red), unconsciousness, death.
Treatment: 100% O₂ (displaces CO from Hb); hyperbaric O₂ for severe cases.
CO is colourless and odourless — "silent killer" (unlike LPG which has odorant added).
*Why A is wrong:* CO doesn't react with water at physiological pH — CO₂ does (forming H₂CO₃).
*Why C is wrong:* CO is stable in the lungs — it doesn't decompose.
*Why D is wrong:* CO doesn't produce hydrogen cyanide — cyanide poisoning has a different mechanism (binds cytochrome oxidase).
Environmental Chemistry
Q181EasyBPSC Prelims
The main cause of acid rain is:
AExcess CO₂ in the atmosphere
BSulphur dioxide (SO₂) and nitrogen oxides (NOₓ) dissolving in rainwater
COzone depletion in the stratosphere
DMethane emissions from paddy fields
Show Answer
✔ B — Sulphur dioxide (SO₂) and nitrogen oxides (NOₓ) dissolving in rainwater
Acid rain: precipitation with pH < 5.6 (normal rain is pH 5.6 due to dissolved CO₂ forming weak carbonic acid).
Causes:
- SO₂ from: coal burning, thermal power plants, volcanic eruptions
SO₂ + H₂O → H₂SO₃ (sulphurous acid) → H₂SO₄ (sulphuric acid)
- NOₓ from: vehicle exhausts, industrial combustion
2NO₂ + H₂O → HNO₂ + HNO₃ (nitrous and nitric acids)
Effects: damages forests (Chota Nagpur), corrodes buildings (Taj Mahal marble pitting), acidifies lakes (kills fish), destroys soil.
*Why A is wrong:* CO₂ does form weak carbonic acid (pH ~5.6) — but that's normal rain, not "acid rain" (pH < 5.6).
*Why C is wrong:* Ozone depletion → increased UV radiation, not acid rain.
*Why D is wrong:* CH₄ from paddy fields = greenhouse gas (not acid rain cause).
Causes:
- SO₂ from: coal burning, thermal power plants, volcanic eruptions
SO₂ + H₂O → H₂SO₃ (sulphurous acid) → H₂SO₄ (sulphuric acid)
- NOₓ from: vehicle exhausts, industrial combustion
2NO₂ + H₂O → HNO₂ + HNO₃ (nitrous and nitric acids)
Effects: damages forests (Chota Nagpur), corrodes buildings (Taj Mahal marble pitting), acidifies lakes (kills fish), destroys soil.
*Why A is wrong:* CO₂ does form weak carbonic acid (pH ~5.6) — but that's normal rain, not "acid rain" (pH < 5.6).
*Why C is wrong:* Ozone depletion → increased UV radiation, not acid rain.
*Why D is wrong:* CH₄ from paddy fields = greenhouse gas (not acid rain cause).
Q182MediumBPSC Prelims
The ozone layer is found in which layer of the atmosphere?
ATroposphere (0–12 km)
BStratosphere (12–50 km)
CMesosphere (50–80 km)
DThermosphere (80–700 km)
Show Answer
✔ B — Stratosphere (12–50 km)
Ozone layer: concentrated in the stratosphere (20–30 km altitude), where ozone (O₃) absorbs harmful UV-B and UV-C radiation from the sun.
Atmospheric layers (from Earth outward):
1. Troposphere (0–12 km): weather occurs, most water vapour, temperature decreases with altitude
2. Stratosphere (12–50 km): ozone layer, temperature INCREASES with altitude (O₃ absorbs UV)
3. Mesosphere (50–80 km): coldest layer, meteors burn up here
4. Thermosphere (80–700 km): very hot (thin air), auroras, ISS orbit
5. Exosphere: outer boundary
*Why A is wrong:* Troposphere contains 90% of atmosphere's mass — ozone forms here too (as a pollutant from photochemical smog) but the protective layer is in the stratosphere.
*Why C is wrong:* Mesosphere — coldest layer, meteors burn up, no significant ozone.
*Why D is wrong:* Thermosphere — extremely hot, very thin air, ionosphere, satellites.
Atmospheric layers (from Earth outward):
1. Troposphere (0–12 km): weather occurs, most water vapour, temperature decreases with altitude
2. Stratosphere (12–50 km): ozone layer, temperature INCREASES with altitude (O₃ absorbs UV)
3. Mesosphere (50–80 km): coldest layer, meteors burn up here
4. Thermosphere (80–700 km): very hot (thin air), auroras, ISS orbit
5. Exosphere: outer boundary
*Why A is wrong:* Troposphere contains 90% of atmosphere's mass — ozone forms here too (as a pollutant from photochemical smog) but the protective layer is in the stratosphere.
*Why C is wrong:* Mesosphere — coldest layer, meteors burn up, no significant ozone.
*Why D is wrong:* Thermosphere — extremely hot, very thin air, ionosphere, satellites.
Q183MediumBPSC Prelims
CFCs (Chlorofluorocarbons) are responsible for:
AAcid rain formation
BOzone layer depletion
CGlobal warming only (not ozone depletion)
DFormation of smog in cities
Show Answer
✔ B — Ozone layer depletion
CFCs: synthetic compounds (CCl₃F, CCl₂F₂, etc.) used in:
- Refrigerators and air conditioners (refrigerants)
- Aerosol propellants
- Foam insulation
Ozone depletion mechanism:
CFCs → hv (UV light in stratosphere) → releases Cl atoms
Cl + O₃ → ClO + O₂
ClO + O → Cl + O₂ (Cl is regenerated → chain reaction)
One Cl atom can destroy thousands of O₃ molecules.
CFCs are ALSO potent greenhouse gases (10,000× more powerful than CO₂).
Montreal Protocol (1987): international treaty banning CFC production.
*Why A is wrong:* Acid rain = SO₂ and NOₓ (not CFCs).
*Why C is wrong:* CFCs cause BOTH ozone depletion AND global warming.
*Why D is wrong:* Smog = photochemical smog (NOₓ + hydrocarbons + sunlight → O₃ in troposphere, PAN, etc.) — CFCs are not primary smog contributors.
- Refrigerators and air conditioners (refrigerants)
- Aerosol propellants
- Foam insulation
Ozone depletion mechanism:
CFCs → hv (UV light in stratosphere) → releases Cl atoms
Cl + O₃ → ClO + O₂
ClO + O → Cl + O₂ (Cl is regenerated → chain reaction)
One Cl atom can destroy thousands of O₃ molecules.
CFCs are ALSO potent greenhouse gases (10,000× more powerful than CO₂).
Montreal Protocol (1987): international treaty banning CFC production.
*Why A is wrong:* Acid rain = SO₂ and NOₓ (not CFCs).
*Why C is wrong:* CFCs cause BOTH ozone depletion AND global warming.
*Why D is wrong:* Smog = photochemical smog (NOₓ + hydrocarbons + sunlight → O₃ in troposphere, PAN, etc.) — CFCs are not primary smog contributors.
Q184MediumBPSC Prelims
Photochemical smog is primarily produced by:
ASulphur dioxide and carbon from coal combustion
BNOₓ and VOCs reacting with sunlight to form ozone and PAN in the lower atmosphere
CWater vapour mixing with industrial dust particles
DCO₂ and methane trapping heat near the ground
Show Answer
✔ B — NOₓ and VOCs reacting with sunlight to form ozone and PAN in the lower atmosphere
Photochemical smog (Los Angeles type): formed by photochemical reactions in sunlight.
Components:
- Primary pollutants: NOₓ (vehicle exhausts), Volatile Organic Compounds (VOCs, hydrocarbons from vehicle exhausts and industries)
- Secondary pollutants (formed by reactions):
- Ground-level ozone (O₃): NO₂ + sunlight → NO + O; O + O₂ → O₃
- PAN (Peroxyacetyl Nitrate): lachrymatory (causes eye irritation)
- Formaldehyde, acrolein (respiratory irritants)
Conditions: sunny weather, slow wind, high vehicle density → Patna, Delhi experience this.
*Why A is wrong:* SO₂ + soot = London smog (classical/sulphurous smog from coal burning) — different from photochemical smog.
*Why C is wrong:* Water vapour + dust = fog/haze, not smog.
*Why D is wrong:* CO₂ and CH₄ = greenhouse gases (global warming, not local smog).
Components:
- Primary pollutants: NOₓ (vehicle exhausts), Volatile Organic Compounds (VOCs, hydrocarbons from vehicle exhausts and industries)
- Secondary pollutants (formed by reactions):
- Ground-level ozone (O₃): NO₂ + sunlight → NO + O; O + O₂ → O₃
- PAN (Peroxyacetyl Nitrate): lachrymatory (causes eye irritation)
- Formaldehyde, acrolein (respiratory irritants)
Conditions: sunny weather, slow wind, high vehicle density → Patna, Delhi experience this.
*Why A is wrong:* SO₂ + soot = London smog (classical/sulphurous smog from coal burning) — different from photochemical smog.
*Why C is wrong:* Water vapour + dust = fog/haze, not smog.
*Why D is wrong:* CO₂ and CH₄ = greenhouse gases (global warming, not local smog).
Q185HardBPSC Prelims
Eutrophication of water bodies occurs when:
AHeavy metals like lead and mercury accumulate in water
BExcess nutrients (nitrogen, phosphorus from fertilizers/sewage) cause algal bloom → oxygen depletion
CIndustrial effluents raise water temperature
DpH drops below 4 due to acid rain
Show Answer
✔ B — Excess nutrients (nitrogen, phosphorus from fertilizers/sewage) cause algal bloom → oxygen depletion
Eutrophication: process by which water body becomes enriched in dissolved nutrients (N, P), stimulating excessive plant/algae growth (algal bloom).
Sequence:
1. Agricultural runoff/sewage → excess N and P in water
2. Algal bloom: rapid multiplication of algae on surface
3. Algae block sunlight → aquatic plants die
4. Dead algae decompose: aerobic bacteria consume O₂
5. BOD increases (Biochemical Oxygen Demand); dissolved O₂ depletes
6. Fish kills and death of other aquatic organisms (hypoxic/anoxic zone)
7. Water becomes turbid, smelly → ecosystem collapse
*Why A is wrong:* Heavy metal accumulation = chemical contamination (different problem).
*Why B is wrong:* Wait — B is the correct answer.
*Why C is wrong:* Thermal pollution (hot water) is a different problem.
*Why D is wrong:* Acidification from acid rain kills aquatic life differently (pH changes affect physiology).
Sequence:
1. Agricultural runoff/sewage → excess N and P in water
2. Algal bloom: rapid multiplication of algae on surface
3. Algae block sunlight → aquatic plants die
4. Dead algae decompose: aerobic bacteria consume O₂
5. BOD increases (Biochemical Oxygen Demand); dissolved O₂ depletes
6. Fish kills and death of other aquatic organisms (hypoxic/anoxic zone)
7. Water becomes turbid, smelly → ecosystem collapse
*Why A is wrong:* Heavy metal accumulation = chemical contamination (different problem).
*Why B is wrong:* Wait — B is the correct answer.
*Why C is wrong:* Thermal pollution (hot water) is a different problem.
*Why D is wrong:* Acidification from acid rain kills aquatic life differently (pH changes affect physiology).
Q186HardBPSC Prelims
The Minamata disease is caused by:
AArsenic contamination of groundwater
BLead poisoning from industrial paint
CMercury poisoning from industrial effluents in water
DFluoride excess in drinking water
Show Answer
✔ C — Mercury poisoning from industrial effluents in water
Minamata disease (Japan, 1956): caused by methylmercury (organic mercury) poisoning from industrial effluents.
- Chisso Corporation discharged mercury waste into Minamata Bay
- Fish accumulated methylmercury (biomagnification)
- Residents eating contaminated fish developed: tremors, sensory loss, coordination problems, birth defects, death
- 2,265 certified victims; thousands more affected
Mercury bioaccumulation in food chain: water → phytoplankton → zooplankton → small fish → large fish → humans (each level concentrates mercury 10-100×)
*Why A is wrong:* Arsenic contamination → arsenicosis (skin lesions, cancer) — endemic in West Bengal/Bihar's Gangetic plain. Different disease.
*Why B is wrong:* Lead poisoning → learning disabilities, brain damage (Saturnism/plumbism) — different disease.
*Why D is wrong:* Fluoride excess → fluorosis (dental/skeletal) — endemic in Rajasthan, parts of Bihar. Different disease.
- Chisso Corporation discharged mercury waste into Minamata Bay
- Fish accumulated methylmercury (biomagnification)
- Residents eating contaminated fish developed: tremors, sensory loss, coordination problems, birth defects, death
- 2,265 certified victims; thousands more affected
Mercury bioaccumulation in food chain: water → phytoplankton → zooplankton → small fish → large fish → humans (each level concentrates mercury 10-100×)
*Why A is wrong:* Arsenic contamination → arsenicosis (skin lesions, cancer) — endemic in West Bengal/Bihar's Gangetic plain. Different disease.
*Why B is wrong:* Lead poisoning → learning disabilities, brain damage (Saturnism/plumbism) — different disease.
*Why D is wrong:* Fluoride excess → fluorosis (dental/skeletal) — endemic in Rajasthan, parts of Bihar. Different disease.
Q187MediumBPSC Prelims
The BOD (Biochemical Oxygen Demand) is used to measure:
AThe amount of dissolved oxygen in water
BThe amount of oxygen consumed by microorganisms to decompose organic matter in water
CThe biological diversity of aquatic organisms
DThe total dissolved solids in water
Show Answer
✔ B — The amount of oxygen consumed by microorganisms to decompose organic matter in water
BOD (Biochemical Oxygen Demand): the amount of dissolved oxygen consumed by biological organisms when decomposing organic matter in water at a certain temperature (usually 20°C, over 5 days — BOD₅).
Higher BOD = more organic pollution = less dissolved oxygen available for aquatic life
BOD standards:
- Clean water: BOD < 3 mg/L
- Acceptable: BOD < 5 mg/L
- Polluted: BOD > 6 mg/L
- Sewage: BOD 100-300 mg/L
Ganga River BOD at different points varies from ~2 mg/L (upstream, clean) to >10 mg/L (near industrial/sewage discharge points).
*Why A is wrong:* Dissolved oxygen (DO) is a separate measurement (mg/L O₂ actually present) — not BOD.
*Why C is wrong:* Biodiversity is measured by species counts, not BOD.
*Why D is wrong:* Total Dissolved Solids (TDS) = measure of all dissolved substances (measured separately by conductivity/evaporation).
Higher BOD = more organic pollution = less dissolved oxygen available for aquatic life
BOD standards:
- Clean water: BOD < 3 mg/L
- Acceptable: BOD < 5 mg/L
- Polluted: BOD > 6 mg/L
- Sewage: BOD 100-300 mg/L
Ganga River BOD at different points varies from ~2 mg/L (upstream, clean) to >10 mg/L (near industrial/sewage discharge points).
*Why A is wrong:* Dissolved oxygen (DO) is a separate measurement (mg/L O₂ actually present) — not BOD.
*Why C is wrong:* Biodiversity is measured by species counts, not BOD.
*Why D is wrong:* Total Dissolved Solids (TDS) = measure of all dissolved substances (measured separately by conductivity/evaporation).
Q188HardBPSC Prelims
Bioaccumulation and biomagnification are different because:
ABioaccumulation occurs in water; biomagnification occurs in air
BBioaccumulation is accumulation of toxins in one organism; biomagnification is increasing concentration of toxins up the food chain
CBioaccumulation only affects plants; biomagnification only affects animals
DBioaccumulation causes acute poisoning; biomagnification causes no harm
Show Answer
✔ B — Bioaccumulation is accumulation of toxins in one organism; biomagnification is increasing concentration of toxins up the food chain
Bioaccumulation: concentration of a substance (e.g., DDT, mercury) within a single organism — more is absorbed than is excreted.
Biomagnification: increasing concentration of a persistent substance at each successive level of the food chain.
Example (DDT in ecosystem):
- Water: 0.000003 ppm
- Phytoplankton: 0.04 ppm (×13,000)
- Small fish: 0.5 ppm (×167,000)
- Large fish: 2 ppm (×667,000)
- Fish-eating birds: 25 ppm (×8 million)
Result: top predators (eagles, humans) receive extremely concentrated doses despite low environmental levels.
*Why A is wrong:* Both can occur in any medium — air, water, soil, organisms.
*Why C is wrong:* Both affect all organisms in a food chain — plants, animals, and humans.
*Why D is wrong:* Biomagnification causes serious harm to top predators (DDT → eagle eggshell thinning → population crash).
Biomagnification: increasing concentration of a persistent substance at each successive level of the food chain.
Example (DDT in ecosystem):
- Water: 0.000003 ppm
- Phytoplankton: 0.04 ppm (×13,000)
- Small fish: 0.5 ppm (×167,000)
- Large fish: 2 ppm (×667,000)
- Fish-eating birds: 25 ppm (×8 million)
Result: top predators (eagles, humans) receive extremely concentrated doses despite low environmental levels.
*Why A is wrong:* Both can occur in any medium — air, water, soil, organisms.
*Why C is wrong:* Both affect all organisms in a food chain — plants, animals, and humans.
*Why D is wrong:* Biomagnification causes serious harm to top predators (DDT → eagle eggshell thinning → population crash).
Q189HardBPSC Prelims
The Kyoto Protocol (1997) and Paris Agreement (2015) both address:
AOzone layer depletion
BMarine pollution from plastic
CGreenhouse gas emission reduction to combat climate change
DElimination of DDT and persistent organic pollutants
Show Answer
✔ C — Greenhouse gas emission reduction to combat climate change
Kyoto Protocol (1997): First international treaty binding developed countries to reduce greenhouse gas emissions (CO₂, CH₄, N₂O, HFCs, PFCs, SF₆) below 1990 levels. US never ratified; Canada withdrew.
Paris Agreement (2015, COP21): Successor agreement — 196 parties including US, China, India.
- Goal: Limit global warming to well below 2°C (ideally 1.5°C) above pre-industrial levels
- NDCs (Nationally Determined Contributions): each country sets its own targets
- India's NDC: 45% reduction in emission intensity by 2030 vs. 2005; net zero by 2070
*Why A is wrong:* Ozone = Montreal Protocol (1987) — different treaty.
*Why B is wrong:* Marine plastic = no comprehensive global treaty yet (UNEA working on it as of 2024).
*Why D is wrong:* POPs (DDT etc.) = Stockholm Convention (2001).
Paris Agreement (2015, COP21): Successor agreement — 196 parties including US, China, India.
- Goal: Limit global warming to well below 2°C (ideally 1.5°C) above pre-industrial levels
- NDCs (Nationally Determined Contributions): each country sets its own targets
- India's NDC: 45% reduction in emission intensity by 2030 vs. 2005; net zero by 2070
*Why A is wrong:* Ozone = Montreal Protocol (1987) — different treaty.
*Why B is wrong:* Marine plastic = no comprehensive global treaty yet (UNEA working on it as of 2024).
*Why D is wrong:* POPs (DDT etc.) = Stockholm Convention (2001).
Environmental Chemistry — Bihar Industrial Chemistry
Q190HardBPSC Prelims
Bihar's main industry in Barauni is based on which raw material and produces which output?
ACoal → Steel (Barauni Steel Plant)
BCrude oil → Petroleum products (Indian Oil Corporation Barauni Refinery)
CLimestone → Cement (Barauni Cement Factory)
DNatural gas → Explosives (Barauni Ordnance Factory)
Show Answer
✔ B — Crude oil → Petroleum products (Indian Oil Corporation Barauni Refinery)
Barauni Oil Refinery (Indian Oil Corporation, Begusarai district, Bihar):
- Established: 1964 — one of India's first public sector refineries
- Raw material: Crude oil (received via Naharkatiya-Barauni pipeline from Assam)
- Products: LPG, petrol, diesel, kerosene, aviation fuel, naphtha, bitumen, sulphur
- Capacity: ~6 million metric tonnes per annum (MMTPA)
Barauni is also known for:
- BVFC (Barauni Fertilizer and Chemical Limited): produces urea fertilizers using ammonia (Haber process)
- HPCL (Hindustan Petroleum): distributes petroleum products from Barauni
*Why A is wrong:* Steel plant = Bokaro (Jharkhand), Rourkela, Bhilai, Durgapur — not Barauni.
*Why C is wrong:* Cement = Rohtas, Wankaner (Bihar limestone areas) — not Barauni.
*Why D is wrong:* Ordnance = Bihar has Munger Gun Factory — not Barauni.
- Established: 1964 — one of India's first public sector refineries
- Raw material: Crude oil (received via Naharkatiya-Barauni pipeline from Assam)
- Products: LPG, petrol, diesel, kerosene, aviation fuel, naphtha, bitumen, sulphur
- Capacity: ~6 million metric tonnes per annum (MMTPA)
Barauni is also known for:
- BVFC (Barauni Fertilizer and Chemical Limited): produces urea fertilizers using ammonia (Haber process)
- HPCL (Hindustan Petroleum): distributes petroleum products from Barauni
*Why A is wrong:* Steel plant = Bokaro (Jharkhand), Rourkela, Bhilai, Durgapur — not Barauni.
*Why C is wrong:* Cement = Rohtas, Wankaner (Bihar limestone areas) — not Barauni.
*Why D is wrong:* Ordnance = Bihar has Munger Gun Factory — not Barauni.