Question

Consider the following unbalanced redox reaction

CrO₄^2- + (CH₃)H + H⁺ → Cr³⁺ + HCOOH + H₂O

Which of the following statements is/are correct?

1.CrO₄^2- is the oxidizing agent.

2. The oxidation number of Cr is decreased in the redox reaction.

3. Electrons are released from CrO₄^2-

• A. 1 only
• B. 1 & 3 only
• C. 2 & 3 only
• D. 1 & 2 only
• E. all

Answer 1

CrO42- + (CH3)H + H+ → Cr3+ + HCOOH + H2O

The oxidation number of Cr in CrO42-

Let Oxidation Number of Cr =X

(Cro4)=-2

X+(-2*4)=-2( Oxidation Number of oxygen is -2)

X=+6,

The oxidation number of Cr in CrO42-=+6

Now create the Skelton equation for this reaction including oxidation number

1.CrO42- is the oxidizing agent

A) True (Oxidising agent itself undergoes reduction. The oxidation number of Cr is decreased by 3 in this reaction , hence Cr undergoes reduction. So it is an oxidizing agent.)

2. The oxidation number of Cr is decreased in the redox reaction.

A) True (The oxidation number of Cr is decreased by 3 in this reaction)

3. Electrons are released from CrO42-

A) False (The oxidation number of Cr is decreased by 3 in this reaction means a Cr undergoes reduction)

(Oxidation: It is the process in which electrons are lost

Reduction: It is the process in which electrons are gained)

Only the statement 1&2 are correct

The answer is option D