Aluminium displaces hydrogen from dilute HCl whereas silver does not. The e.m.f. of a cell prepared by combining Al/Al3+ and Ag/Ag+ is 2.46 V. The reduction potential of silver electrode is + 0.80 V. The reduction potential of aluminium electrode is

EMF is positive cell reaction is spontaneous indicates that SRP of cathode is greater than SRP of anode or SOP of anode is greater than SOP of cathode EMF = SOP of anode - SOP of cathode Ag electrode must be cathode and Al electrode must be anode EMF = EAl/Al+3° - EAg/Ag+°2.46 = EAl/Al+3°-(-0.8)2.46 - 0.8 = EAl/Al+3°EAl/Al+3°= 1.66 VEAl+3/Al° =-EAl/Al+3°=- 1.66V