Question

A cell consists of two hydrogen electrodes, the negative electrode has $\left[H^{+}\right]={10}^{-7}M$. Find the minimum pH of the other electrode at which, the cell reaction will be spontaneous.
(Consider both cells have equal $H_2\left(g\right)$ pressure)

• A. Less than 7
• B. Greater than 7
• C. Can not calculated
• D. Can have any value
• E. Blank

Answer 1

Answer: (E)

Blank

Since both $-ve$ as well as $+ve$ electrode is made up of same material.

It is a ${conc}^n$ cell

$-ve$ electrode means anode ${\left[H^{+}\right]}_A={10}^{-7}M$

$E_{cell}=0-\frac{0.0591}{1}log\frac{{\left[H^{+}\right]}_A}{{\left[H^{+}\right]}_C}=0-\frac{0.0591}{1}log\frac{{10}^{-7}}{{\left[H^{+}\right]}_C}$

${\left[H^{+}\right]}_C>{10}^{-7}$ (for spontaneous )

so $pH<7$