Question

Which one of the following combinations of reagents will result in a spontaneous reaction?
A) Al(s) + CuCl2(aq)
B) Al(s) + CaCl2(aq)
C) Zn(s) + CaCl2(aq)
D) Cu(s) + ZnCl2(aq)


I know the answer is A, but what I don't know is why, or how to figure this out. Thanks!

Answer 1

Look at the activity series of metals.
A metal will displace an ION below it in the activity series. And that is a spontaneous reaction.

http://www.files.chem.vt.edu/RVGS/ACT/notes/activity_series.html
For example, Zn metal will displace Cu^+2 ion in the reaction
Zn + CuCl2 ==> Cu + ZnCl2

But a metal will NOT displace the ION of a metal above it in the activity series.
CuCl2 + Zn ==> no reaction.