Question

The dichromate ion is reduced by the chloride ion in acidic solution. Balance the reaction from the skeleton equation using the half-reaction method.

Cr₂O₇²⁻ + Cl⁻ ➝ Cr³⁺ + Cl₂
What is the coefficient for Cr₂O₇²⁻ in the balanced net ionic equation?

Answer 1

The coefficient for Cr2O7²− in the balanced net ionic equation is 1.

Step-by-step explanation:

To balance the reaction between the dichromate ion (Cr2O72−) and chloride ion (Cl−) in acidic solution, we need to find the coefficient for Cr2O72− in the balanced net ionic equation. Using the half-reaction method, we split the reaction into two half-reactions. First, the reduction half-reaction where Cr2O72− is reduced to Cr3+, and second, the oxidation half-reaction where Cl− is oxidized to Cl2.

For the reduction half-reaction, we balance the chromium atoms:

Cr2O72− (aq) → 2Cr3+ (aq)

Then we add 14H+ to the reactant side to balance the oxygen atoms and form 7H2O on the product side:

14H+ (aq) + Cr2O72− (aq) → 2Cr3+ (aq) + 7H2O (l)

Finally, to balance the charges, we add 6 electrons to the reactant side because there is a total charge of 6+ on the product side (2 Cr3+) and a total charge of 12+ on the reactant side (Cr2O72− and 14H+):

6e− + 14H+ (aq) + Cr2O72− (aq) → 2Cr3+ (aq) + 7H2O (l)

The balanced reduction half-reaction shows that the coefficient for Cr2O72− is 1 in the balanced net ionic equation.