Answer:
Cr(s) ⟶ Cr⁴⁺(aq) + 4e⁻
Explanation:
1. Write the skeleton half-reaction
Cr(s) ⟶ Cr⁴⁺(aq)
2. Balance charge
Add electrons to the side that needs them.
You have 4+ on the right and 0 on the left. You must add 4e⁻ to the right to balance the charge.
Cr(s) ⟶ Cr⁴⁺(aq) + 4e⁻
