Question

If hydrogen electrode dipped in $2$ solution of $pH=3$ and $pH=6$ and salt bridge is connected the emf of resulting cell is:

• A. 0,177V
• B. - 0.3V
• C. 0.052V
• D. 0.104V

Answer 1

Answer: (A)

For concentration cells
$E_{\text{cell }}^o=\frac{0.0591}{1}\log \left[\frac{\text{ anode }}{\text{ cathode }}\right]$
The electrode having lower concentration acts as anode and the electrode having higher concentration acts as cathode.
The cells having same electrolytes at cathode and anode are called concentration cells.
Given: $pH=3$ for first solution and $pH=6$ for second solution. $\left[H^{+}\right]$for first solution
$=10^{-pH}=10^{-3}\left[H^{+}\right]$ for second solution
$=10^{-pH}=10^{-6}$
$\therefore E_{\text{cell }}^o=-\frac{0.0591}{1}\log \left[\frac{10^{-6}}{10^{-3}}\right]$
$=0.091\log 10^{-3}=-0.0591\times (-3\log 10)$
$=-0.0591\times (-3\times 1)=-0.0591-3$
$\therefore E_{\text{cell }}^o=0.177V$