1. The correct option for a redox couple is:⇒ (NEET 2023 Manipur)

A. Both are oxidised forms involving same element.

B. Both are reduced forms involving same element.

C. Both the reduced and oxidised forms involve same element.

D. Cathode and anode together.

The Correct Answer is Option (C)

Redox couple is both the reduced and oxidised form involve same element.

2. Hot concentrated sulphate acid is a moderately strong oxidizing agent. Which of the following reactions does not show oxidizing behaviour? ⇒ (NEET 2016 Phase II)

A. Cu + 2H₂SO₄ $\to$ CuSO₄ + SO₂ + 2H₂O

B. S + 2H₂SO₄ $\to$ 3SO₂ + 2H₂O

C. C + 2H₂SO₄ $\to$ CO₂ + 2SO₂ + 2H₂O

D. CaF₂ + H₂SO₄ $\to$ CaSO₄ + 2HF

The correct answer is option (D)

CaF₂ + H₂SO₄ $\to$ CaSO₄ + 2HF

Here, the oxidation state of every atom remains the same so, it is not a redox reaction.

3. (I) H₂O₂ + O₃ $\to$ H₂O + 2O₂
(II) H₂O₂ + Ag₂O $\to$ 2Ag + H₂O + O₂
Role of Hydrogen peroxide in the above reactions is respectvely ⇒ (AIPMT 2014)

A. oxidizing in (I) and reducing in (II)

B. reducing in (I) and oxidizing (II)

C. reducing in (I) and (II)

D. oxidizing in (I) and (II)

The correct answer is option (C)

AIPMT 2014 Chemistry - Redox Reactions Question 16 English Explanation

So, H₂O₂ acts as reducing agent in all those reactions in which O₂ is evolved.

4. The pair of compounds that can exist together is ⇒ (AIPMT 2014)

A. FeCl₃, SnCl₂

B. HgCl₂, SnCl₂

C. FeCl₂, SnCl₂

D. FeCl₃, KI

The correct answer is option (C)

Both FeCl₂ and SnCl₂ are reducing agents with low oxidation numbers.

5. Which is the best description of the behaviour of bromine in the reaction given below?
H₂O + Br₂ $\to$ HOBr + HBr ⇒ (AIPMT 2004)

A. Proton acceptor only

B. Both oxidised and reduced

C. Oxidised only

D. Reduced only

The correct answer is option (B)

H₂O + $\overset{0}{B r}$ ₂ $\to$ HO $\overset{+ 1}{B r}$ + H $\overset{- 1}{B r}$

In the above reaction the oxidation number of Br₂ increases from zero (in Br₂ ) to +1 (in HOBr) and decreases from zero (in Br₂ ) to –1 (in HBr). Thus Br₂ is oxidised as well as reduced and hence it is a redox reaction.

6. The oxide which cannot act as a reducing agent is ⇒ (25 April 2013(Online))

A. CO₂

B. ClO₂

C. NO₂

D. SO₂

The correct answer is option (A)

CO₂ cannot act as reducing agent because C in CO₂ has an oxidation state of +4 . C can have a maximum of +4 oxidation state, it cannot increase the oxidation state beyond +4 thus CO₂ cannot undergo oxidation thus it cannot act as a reducing agent.

7. Which species is acting as a reducing agent in the following reaction ?
14H⁺ + Cr₂O₇^2- → 2Cr³⁺ + 7H₂O + 3Ni²⁺ ⇒ ()

A. Cr₂O₇^2-

B. Ni

C. H⁺

D. H₂O

The correct answer is option (B)

Reducing agent is define as the species which carries out the reduction of other species and itself gets oxidized.
In the reaction given in option B, the charge on nickel atom is changed from 0 to +2. Thus Nickel atom is oxidized and it carries on nickel out the reduction of Chromium atom.
14H⁺ + Cr₂O₇^2- → 2Cr³⁺ + 7H₂O + 3Ni²⁺
Oxidation: Ni ⇒ Ni²⁺
Reduction: Cr⁶⁺ ⇒ Cr³⁺

⇒Redox

Topic 7 : Oxidizing and Reducing Agent in Reaction