an electrochemical cell uses Al and Al+3 in one compartment and Ag and Ag+ in the other

write a balanced equation for the rxn that will occur spontaneously in this cell

would that just be Al + Al+3 + 2e --> Ag + Ag+ ?

1 answer

Not quite.
The half equations you want are as follows:
Al ==> Al^+3 + 3e
Ag^+ + e ==> Ag
=================
Multiply equation 1 by 1 and equation 2 by 3 (to make the electrons equal).
Al ==> Al^+3 + 3e
3Ag^+ + 3e ==> 3Ag
===================
Now add them.
Al + 3Ag^+ + 3e ==> Al^+3 + 3e + 3Ag
Now cancel the electrons (since there are 3 on each side). That gives you the final equation.