Final answer:
To balance the Cl₂ + Cr³⁺ → Cr₂O₇²⁻ + Cl⁻ reaction, use the half-reaction method. Upon balancing, the correct coefficient for Cl₂ is 5, resulting in a balanced equation showing the interaction between these species in an acidic solution.
Step-by-step explanation:
The student has asked to balance the unbalanced redox reaction Cl₂ + Cr³⁺ → Cr₂O₇²⁻ + Cl⁻ in an acidic solution and to indicate the coefficient for Cl₂. To balance this reaction, we'll follow the half-reaction method, which involves balancing the oxidation and reduction reactions separately.
Let's start by identifying the two half-reactions. For the oxidation part, Cl₂ is reduced to Cl⁻, and for the reduction part, Cr³⁺ is oxidized to Cr₂O₇²⁻. Next, we balance all the elements except oxygen and hydrogen, and then balance the oxygen atoms by adding H₂O and the hydrogen atoms by adding H⁺ ions. Finally, we balance the charges by adding electrons to the half-reactions.
After calculating, we find that the coefficient for Cl₂ in this reaction is 5. Therefore, the balanced reaction is 5 Cl₂ + 6 Cr³⁺ + 14 H⁺ → 2 Cr₂O₇²⁻ + 10 Cl⁻ + 7 H₂O.