Question

Which of the following ions can be reduced from an aqueous solution?

A)Ba2+
B)Al3+
C)Sn2+
D)Na+

Do I look for the higher volts? Thanks in advance.

Answer 1

You want to look for the ion that, when combined with the H2O couple, will have a positive voltage. You can make some good guesses without looking at the voltage table. For example,(from the activity series) I know Na reacts with H2O (Ba metal also) vigorously; therefore, I wouldn't expect that we could electrolyze Na^+ or Ba^+2 to the metal. Where are Al and Sn in the activity series? [But note that the activity series is comparing with H^+, not water].