Indicate what reaction is happening at the anode, and for the reaction below, which species would be the anode? Sn(s) + 2 Ag⁺(aq) → Sn2+(aq) + 2 Ag(s)

Sn --> Sn2+ + 2e-

Explanation:

At anode oxidation reaction occur. In this reaction Sn is getting oxidized to state +2 while Ag is reduced from +1 to 0.

Hence, reaction at anode will be  

Sn (s) --> Sn2+ (aq) + 2e-

At cathode the following reaction occur

2 Ag⁺ + 2e- ---> 2Ag (s)

yes the answer is total mass in unchanged   : )