Answer:
3) Mg to Al3+
Explanation:
The given reaction is:
\(2Al^{3+} (aq) + 3Mg(s) ---- 3Mg^{2+} (aq) + 2Al(s)\)
This is an example of a redox reaction i.e. a reduction-oxidation reaction which involves transfer of electrons between Al and Mg.
Reduction involves gain of electrons, whereas oxidation involves loss of electrons. The two half reactions can be depicted as shown below:
Oxidation:
\(Mg(s) ----- Mg^{2+} + 2e-\)
Reduction:
\(Al^{3+} (aq) + 3e- ---- Al(s)\)
Thus Mg loses electrons and gets oxidised to Mg2+
whereas Al3+ gains electrons and gets reduced to Al3+
