Question

Which is not true for a standard hydrogen electrode? (1) The hydrogen ion concentration is \(1 \mathrm{M}\) (2) Temperature is \(25^{\circ} \mathrm{C}\) (3) Pressure of hydrogen gas is 1 atmosphere (4) It contains a metallic conductor which does not absorb hydrogen

Short answer

All statements are true.

Step-by-step solution

- Identify the standard conditions for a standard hydrogen electrode (SHE)

A standard hydrogen electrode (SHE) operates under specific conditions to serve as a reference electrode. These conditions are a hydrogen ion concentration of 1 M, a temperature of 25°C, and a hydrogen gas pressure of 1 atmosphere.

- Analyze each given statement

Consider each of the given statements and compare them to the standard conditions for SHE: (1) Hydrogen ion concentration is 1 M - this is true.(2) Temperature is 25°C - this is true.(3) Pressure of hydrogen gas is 1 atmosphere - this is true.(4) It contains a metallic conductor which does not absorb hydrogen - this statement needs to be analyzed further.

- Examine the conductor material in SHE

The SHE uses a platinum electrode because platinum does not absorb hydrogen but instead facilitates the gas's involvement in redox reactions. Hence, statement (4) is actually true.

Key concepts

Electrode Conditions

The Standard Hydrogen Electrode (SHE) operates under very specific conditions to ensure consistency and reliability. These conditions include:
- A hydrogen ion concentration of 1 molar (1 M).
- A temperature of 25°C, which is equivalent to 298 Kelvin.
- A pressure of hydrogen gas maintained at 1 atmosphere (atm).
These conditions are critical because they provide a universal reference for measuring the electrode potential of any other electrode. This consistency allows scientists to accurately compare results across different experiments and studies. Without these standardized conditions, the effectiveness and reliability of the SHE would be compromised.

Hydrogen Ion Concentration

One of the fundamental conditions for the Standard Hydrogen Electrode (SHE) is the hydrogen ion concentration. In the SHE, the hydrogen ion concentration must be exactly 1 Molar (1 M).
At a 1 M concentration, there are exactly 1 mole of hydrogen ions (H⁺) per liter of solution. This specific concentration ensures that the electrode operates under standardized conditions each time it is used.
Maintaining this concentration is pivotal for the electrode's function because electrical potential is directly related to the activity of the ions in the solution. Any deviation from the 1 M concentration would result in an inaccurate potential, thereby making the SHE unreliable as a reference.

Platinum Electrode

The SHE uses a platinum electrode for several important reasons. Firstly, platinum is chemically inert, meaning it doesn't react with other substances in the solution. This non-reactivity makes platinum an ideal material because it ensures the integrity of the electrode's measurements.
Secondly, platinum does not absorb hydrogen. This is crucial because an absorbing material would alter the concentration of hydrogen ions and the surface chemistry, leading to inconsistent readings.
Lastly, platinum facilitates the redox reactions involving hydrogen gas. It acts as a catalyst, allowing for a smooth and efficient exchange of electrons. This efficiency is necessary to accurately measure the standard electrode potential.