Answer: 6
Explanation:
Mg (s) + Cr3+ (aq) → Cr (s) + Mg2+ (aq)
Balancing the equation above we have,
3Mg (s) + 2Cr3+ (aq) → 2Cr (s) + 3Mg2+ (aq)
Half reaction
3Mg (s) → 3Mg2+ (aq) +6e-
2Cr3+ (aq) + 6e- → 2Cr (s)
Therefore six electrons were transferred (6e-)