Question

The pressure of H₂ required to make the potential of H₂-electrode zero in pure water at 298 K is ______.

पर्याय

• 10⁻¹⁴ atm

• 10⁻¹² atm

• 10⁻¹⁰ atm

• 10⁻⁴ atm

Answer 1

The pressure of H₂ required to make the potential of H₂-electrode zero in pure water at 298 K is 10⁻¹⁴ atm.

Explanation:

For the standard hydrogen electrode (SHE), the electrode potential is given by the Nernst equation:

E = 0 − 0.0591 pH

In pure water, pH = 7, so:

E = −0.0591 × 7 = −0.4137 V

To make E = 0, we must increase the pressure of H₂, as per the Nernst equation for the hydrogen electrode.

Set E = 0, and use [H⁺] = 10⁻⁷ M

\[\ce{E = 0.0591 log \frac{[H^{+}]^2}{[P_{H_2}]}}\]

\[\ce{0 = 0.0591 log \frac{(10^{-7})^2}{(P_{H_2)}}}\]

⇒ \[\ce{log \frac{10^{-14}}{P_{H_2}}}\] = 0

\[\ce{\frac{10^{-14}}{P_{H_2}}}\] = 0

\[\ce{P_{H_2}}\] = 10⁻¹⁴ atm