Consider the following half-cell reactions.

Al(s) \(\to\) Al3+(aq) + 3e-

Cu2+(aq) + 2e- \(\to\) Cu(s)

The overall equation for the reaction is

  • A Al(s) + Cu2+(aq) \(\to\) Al3+(aq) + Cu(s)
  • B 2Al(s) + Cu2+(aq) \(\to\) 2Al(aq) + Cu(s)
  • C 2Al(s) + 3Cu2+(aq) \(\to\) 3Cu(s) + 2Al3+(aq)
  • D 3Al(s) + 2Cu2+(aq) \(\to\) Cu(s) + 3Al3+(aq)
waec 2016chemistry

The correct answer is C. 2Al(s) + 3Cu2+(aq) \(\to\) 3Cu(s) + 2Al3+(aq)

Al(s) \(\to\) Al3+(aq) + 3e- ______(i)

Cu2+(aq) + 2e- \(\to\) Cu(s) ________(ii)

To balance the electrons, multiply equation (i) by 2 and equation (ii) by 3 and then add the resulting equations

2Al(s) \(\to\)2Al3+(aq) + 3e-

3cu2+(aq) + 6e- \(\to\)3Cu(s)

2Al(s) + 3Cu2+(aq) \(\to\) 3Cu(s) + 2Al3+(aq)

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