1 in the cathode apply the electron so the reaction is the 3rd
2 in the anode absorb the electron so the reaction is the 1st
3 because the solution content acid and the production of the H2O will be react with the acid ,acorrding to the 勒沙特列原理 the production of the H2O absorb the electron become the OH-
4 the Ag's activity of matail lower then H so the reaction is Ag abtain the electron