Question

Write a balanced half-reaction for the reduction of dichromate ion to chromium ion in acidic aqueous solution. Be sure to add physical state symbols where appropriate.

Answer 1

Answer:

The balanced half-reaction for the reduction of dichromate ion to chromium ion in acidic aqueous solution:

$Cr_2O_7^{2-}(aq)+14H^+(aq)+6e^-\rightarrow 2Cr^{3+}(aq)+7H_2O(l)$

Explanation:

The reaction :

$Cr_2O_7^{2-}\rightarrow Cr^{3+}$

Balancing of reaction in an acidic medium:

Step 1: Balance the atoms in the reaction:

$Cr_2O_7^{2-}(aq)\rightarrow 2Cr^{3+}(aq)$

Step 2: Balance oxygen atom by adding water on the side where no oxygen or less oxygen atom is present;

$Cr_2O_7^{2-}(aq)\rightarrow 2Cr^{3+}(aq)+7H_2O(l)$

Step 3: Balance the hydrogen atom by adding  hydrogen ions on the side where water is absent:

$Cr_2O_7^{2-}(aq)+14H^+(aq)\rightarrow 2Cr^{3+}(aq)+7H_2O(l)$

Step 4: Now balance charge by adding electrons on the side where more positive charge is present

$Cr_2O_7^{2-}(aq)+14H^+(aq)+6e^-\rightarrow 2Cr^{3+}(aq)+7H_2O(l)$

The balanced half-reaction for the reduction of dichromate ion to chromium ion in acidic aqueous solution:

$Cr_2O_7^{2-}(aq)+14H^+(aq)+6e^-\rightarrow 2Cr^{3+}(aq)+7H_2O(l)$