The reduction potential of hydrogen half-cell will be negative if : (1) PH2 = 2 atm and [H+] = 2.0 M (2) PH2 = 1 atm and [H+] = 2.0 M (3) PH2 = 1 atm and [H+] = 1.0 M (4) PH2 = 2 atm and [H+] = 1.0 M

  $H+-e-\to \frac{1}{2}H2$   

Apply Nernst equation  

$E=0-\frac{0.059}{1}\log \frac{PH2\frac{1}{2}}{H}$  

  $E=-\frac{0.059}{1}\log \frac{2}{\frac{1}{2}}$  

Therefore E is Negative