Question

The reduction potential of hydrogen half-cell will be negative if :

• A. $p \left( H _{2}\right)=2 atm$ and $\left[ H ^{+}\right]=2.0 M$
• B. $p \left( H _{2}\right)=1 atm$ and $\left[ H ^{+}\right]=2.0 M$
• C. $p \left( H _{2}\right)=1 atm$ and $\left[ H ^{+}\right]=1.0 M$
• D. $p \left( H _{2}\right)=2 atm$ and $\left[ H ^{+}\right]=1.0 M$

Answer 1

Answer: (D)

$H ^{+}+ e ^{-} \longrightarrow \frac{1}{2} H _{2}$

Apply Nernst equation

$E =0 -\frac{0.059}{1} \log \frac{ P _{ H _{2}}^{\frac{1}{2}}}{\left[ H ^{+}\right]}$

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

Therefore $E$ is negative.