NEET Chemistry: Redox reactions and balancing Practice Questions
13 free multiple-choice questions on Redox reactions and balancing (Redox Reactions and Electrochemistry) for NEET Chemistry, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. Which of the following statements correctly defines a reduction reaction?
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Correct answer: D — Loss of oxygen and gain of electrons
Reduction is the gain of electrons (or loss of oxygen). The loss of electrons is oxidation.
Q2. In a redox reaction, oxidation is defined as:
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Correct answer: D — Decrease in oxidation number
Oxidation is the loss of electrons by a species, which corresponds to an increase in its oxidation number.
Q3. When hydrogen peroxide (H₂O₂) is oxidized, the change in its oxidation state is:
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Correct answer: A — +2
In H₂O₂, O is -2. When it is oxidized to O₂, O is 0. The change is 0 - (-2) = +2.
Q4. Which of the following is a reducing agent?
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Correct answer: A — Na
A reducing agent is the species that causes oxidation by getting oxidized itself (losing electrons). Sodium (Na) readily loses an electron to be oxidized. Fe³⁺ is an oxidizing agent, Cl⁻ and O₂ are typically not redox agents in this context.
Q5. Which of the following processes corresponds to oxidation in a redox reaction?
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Correct answer: B — Loss of electrons
Oxidation is the process of loss of electrons by a species, which corresponds to an increase in oxidation number.
Q6. If the concentration of a reactant is doubled in a redox reaction, how does the reaction rate generally change (assuming sufficient time and temperature)?
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Correct answer: A — The reaction rate is doubled.
Increasing the concentration of reactants generally leads to a faster reaction rate because there are more collisions between reactant particles.
Q7. In a redox reaction, the substance that is oxidized is the one that undergoes:
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Correct answer: C — Oxidation
Oxidation is the loss of electrons, which corresponds to an increase in oxidation number. The substance that loses electrons is oxidized.
Q8. Which of the following reactions is a redox reaction?
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Correct answer: A — C + O₂ → CO₂
A redox reaction is a reaction involving the transfer of electrons, which results in a change in the oxidation states of the atoms involved. Option C (MnO₂ → Mn²⁺) involves a change in oxidation state of Manganese (from +4 to +2), making it a redox reaction. Options A, B, and D are typically combination or decomposition reactions, not redox reactions.
Q9. Which statement is true regarding the balancing of redox reactions by the oxidation number method?
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Correct answer: B — The total change in oxidation numbers must be equal on both sides of the equation.
In balancing redox reactions by the oxidation number method, the total change in oxidation numbers for all elements on the reactant side must equal the total change on the product side.
Q10. The oxidation number of Oxygen in H₂O₂ is:
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Correct answer: C — -1
In the compound H₂O₂, Hydrogen has an oxidation state of +1. Let x be the oxidation state of Oxygen. 2(+1) + 2x = 0, so 2x = -2, and x = -1.
Q11. In a redox reaction, oxidation always occurs by:
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Correct answer: C — Loss of electrons
Oxidation is the process of loss of electrons, which corresponds to an increase in the oxidation state of the atom involved.
Q12. Which type of cell involves the spontaneous transfer of electrons from one half-cell to another through an external circuit?
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Correct answer: D — Galvanic (Voltaic) cell
A galvanic or voltaic cell generates electrical energy from a spontaneous redox reaction.
Q13. What is the oxidation state of Chromium (Cr) in potassium dichromate (K₂Cr₂O₇)?
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Correct answer: A — +2
In dichromate (Cr₂O₇²⁻), the total charge is zero. Let Cr be x. 2x + 7(-2) = 0 ⇒ 2x = 14 ⇒ x = +7. Since K⁺ = +1, the oxidation state of Cr is +7.
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