Cell is equivalent to Pt, H2(g)/H+(aq)//H+(aq)/H2(g), Pt10atm 10−9M 10−3M 0.1atm
oxidation half cell:
H2(g)10 atm→2H+10−9 M+2e−
reduction half cell:
2H+(aq.)10−3 M+2e−→H2(g)0.1 atm
overall reaction:
2H+(aq.)10−3 M+H2(g)10 atm→H2(g)0.1 atm+2H+10−9 M
apply nearst equation for n=2
E0cell=0−0.062log(10−9)2×0.110×(10−3)2=−0.062 log 10−14=0.42V