Balancing redox reactions can become quite complicated and a systematic approach should be used. The half-reaction method of balancing redox reactions emphasizes the fact that redox reactions can be separated into an oxidation half-reaction, which shows only the oxidation process and a reduction half-reactions which shows the reduction process. For the overall balanced reaction, the two half-reactions are combined so that the electrons in the two half-reactions cancel. The half-reaction method is particularly useful for reactions in aqueous solution. The two half-reactions are combined to make a balanced redox equation.

1. Which of the following represents a redox reaction?

1. NaOH + HCl → NaCl + H₂O
2. BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl
3. CuSO₄ + 2H₂O → Cu(OH)₂ + H₂SO₃
4. Zn + 2HCl → ZnCl₂ + H₂

Answer: (d)

2. Which reaction involves neither oxidation nor reduction?

1. CrO₄^2- -→ Cr₂O₇^2-
2. Cr → CrCl₃
3. Na → Na⁺
4. 2S₂O₃^2- → S₄O₆^2-

Answer: (a)

3. Zn gives H₂ gas with H₂SO₄ and HCl but not with HNO₃ because

1. Zn acts as an oxidising agent when it reacts with HNO₃
2. HNO₃ is a weaker acid than H₂SO₄ and HCl
3. In electrochemical series, Zn is above hydrogen
4. NO₃^– is reduced in preference to hydronium ion

Answer: (d)

4. A compound of Xe and F is found to have 53.5% of Xe. What is the oxidation number of Xe in this compound?

1. -4
2. 0
3. +4
4. +6

Answer: (d)

5. A solution contains Fe²⁺, Fe³⁺ and I^– ions. This solution was treated with iodine at 35^oC. E^o for Fe³⁺/Fe²⁺ is 0.77V and E^o for I₂/2I^– = 0.536V. The favourable redox reaction is

1. I₂ will be reduced to I^–
2. there will be no redox reaction
3. I^– will be oxidised to I₂
4. Fe²⁺ will be oxidised to Fe³⁺

Answer: (c)

6. One mole of N₂H₄ loses 10 moles of electrons to form a new compound y. Assuming that all nitrogen appears in the new compound, what is the oxidation state of nitrogen in y.

1. -1
2. -3
3. +3
4. +5

Answer: (c)

7. The equivalent mass of oxidising agent in the following reaction is

SO₂ + 2H₂S → 3S + 2H₂O

1. 32
2. 64
3. 16
4. 8

Answer: (c)

8. In the reaction

3Br₂ + 6CO₃^2- + 3H₂O → 5Br^– + BrO₃^– + 6HCO₃^–

1. bromine is oxidised and carbonate is reduced
2. bromine is reduced and water is oxidised
3. bromine is neither reduced nor oxidised
4. bromine is both reduced and oxidised

Answer: (d)

9. Which of the following cannot function as an oxidising agent?

1. I^–
2. Si(s)
3. NO₃^–(aq)
4. Cr₂O₇^2-

Answer: (a)

10. The oxidation number of Pt in [Pt(C₂H₄)Cl₃]^– is

1. +1
2. +2
3. +3
4. +4

Answer: (b)

Consider reading:

• NEET Chemistry Syllabus
• How to Score 160 Plus in NEET Chemistry
• NEET Chemistry Weightage
• Chemistry Formulas for NEET
• NEET Chemistry MCQs
• NEET Chemistry Important Topics