The pressure of `H_(2)` required to make the potential of `H_(2)-`electrode zero in pure water at 289K is :

Options

A. `10^(-10)` atm
B. `10^(-4)` atm
C. `10^(-14) ` atm
D. `10^(-12)` atm

Answer

C

Explanation

For a hydrogen electrode
`2 H^+ (aq) + 2e^- to H_(2) (g)`
`E = E^(@) - (0.059)/(2) "log" (p(H_(2)))/([H^(+)]^(2))`
In pure water at 298 K ,`[H^(+)] = 10^(-7)`
`therefore E = 0- (0.059)/(2) "log" (p(H_(2)))/([10^(-7)]^(2)) = (0.059)/(2) "log" (p(H_(2)))/(10^(-14))`
`therefore` E will be zero when `p(H_(2)) = 10^(-14)` atm