Which of the following is a redox reaction? MCQ with Answer and Explanation

Which of the following is a redox reaction?
A. BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl
B. 2Na + Cl₂ → 2NaCl
C. NaOH + HCl → NaCl + H₂O
D. CaCO₃ → CaO + CO₂
Answer: Option B
Solution (By JKSSB Mock Tests)
In 2Na + Cl₂ → 2NaCl, sodium is oxidized (Na → Na⁺ + e⁻) and chlorine is reduced (Cl₂ + 2e⁻ → 2Cl⁻). It involves change in oxidation states. Options A and B are double displacement (no change in oxidation states). Option D is decomposition with no change in oxidation states (Ca: +2 remains +2). Redox reactions involve simultaneous oxidation and reduction.

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Practice More chemistry Questions

Question #1
The ignition temperature of a fuel is:
A. The lowest temperature at which it catches fire.
B. The temperature at which it melts.
C. The temperature at which it boils.
D. The highest temperature it can reach.

Correct Answer: Option A


Explanation:
The ignition temperature (or kindling temperature) is the minimum temperature to which a fuel must be heated so that it catches fire and starts burning spontaneously. A lower ignition temperature means the fuel is more highly flammable and can ignite more easily at ambient conditions.

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Question #2
The conversion of ethanol to ethene requires:
A. Dehydration
B. Fermentation
C. Oxidation
D. Hydrogenation

Correct Answer: Option A


Explanation:
Ethanol (C₂H₅OH) on heating with excess concentrated H₂SO₄ (dehydrating agent) at 170°C undergoes dehydration to give ethene (C₂H₄). This is an elimination reaction. Oxidation gives ethanoic acid; hydrogenation adds H₂; fermentation produces ethanol.

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Question #3
Which of the following compounds has both ionic and covalent bonds?
A. HCl
B. NaOH
C. CH₄
D. NaCl

Correct Answer: Option B


Explanation:
Sodium hydroxide (NaOH) has ionic bond between Na⁺ and OH⁻, and covalent bond between O and H within OH⁻. NaCl is purely ionic; CH₄ and HCl are purely covalent (polar covalent in HCl, but not ionic).

This question belongs to: Science chemistry