Question

Compare the average temperature coefficients in the range of 15°C to 35°C for the five reference electrodes

listed in Table 23-1.

Short answer

$0.1\mathrm{M}$calomel electrode has least value of temperature coefficient whereas the saturated $\mathrm{Ag}-\mathrm{AgCl}$electrode has highest value of temperature coefficient in the range of $15°\mathrm{C}$ to $35°\mathrm{C}$.

Step-by-step solution

Step 1. Concept Understanding

Potentiometric titration are the simple titration that is used to measure the concentration of the sample. No indicator is required in these titrations.

Step:2 Explanation

The five Electrodes in $23.1$

The formula for calculating the average temperature coefficient is as follows:

$=\frac{\text{Electrode potential at}{35}^{\circ }\mathrm{C}-\text{Electrode potential at}{15}^{\circ }\mathrm{C}}{{35}^{\circ }\mathrm{C}-{15}^{\circ }\mathrm{C}}$

Substitute the electrode potential of $0.1$M calomel electrode at ${15}^{\circ }$C and ${35}^{\circ }C$in equation

$\text{Temperature coefficient}=\frac{(0.3344-0.3362)\mathrm{V}}{{35}^{\circ }\mathrm{C}-{15}^{\circ }\mathrm{C}}$

$=-\frac{0.0018}{20}\mathrm{V}{/}^{\circ }\mathrm{C}$

$=-9.0\times {10}^{-5}\mathrm{V}{/}^{\circ }\mathrm{C}$

Step:3 Substitution.

Substitute the electrode potential of $3.5M$ calomel electrode at ${15}^{\circ }C$and ${35}^{\circ }C$in equation 1

$\text{Temperature coefficient}=\frac{(0.246-0.254)\mathrm{V}}{{35}^{\circ }\mathrm{C}-{15}^{\circ }\mathrm{C}}$

$=-\frac{0.008}{20}\mathrm{V}{/}^{\circ }\mathrm{C}$

$=-4.0\times {10}^{-4}\mathrm{V}{/}^{\circ }\mathrm{C}$

Calculation

Substitute the electrode potential of saturated calomel electrode at ${15}^{\circ }C$and ${35}^{\circ }C$ in equation $1$.

Temperature coefficient $=\frac{(0.2376-0.2511)\mathrm{V}}{35°\mathrm{C}-15°\mathrm{C}}$

$=-\frac{0.0135}{20}\mathrm{V}/{}^{\circ }\mathrm{C}$

= $-6.75\times {10}^{-4}\mathrm{V}/{}^{\circ }\mathrm{C}$

Substitute the electrode potential of localid="1647525830031" $3.5MAg$-localid="1647525837086" $Agcl$ electrode at localid="1648539248895" ${15}^{\circ }C$and localid="1648539262437" ${35}^{\circ }C$in equation (1).

Temperature Coefficient $=\frac{(0.197-0.212)\mathrm{V}}{{35}^{\circ }\mathrm{C}-{15}^{\circ }\mathrm{C}}$

$\begin{array}{c}=-\frac{0.015}{20}\mathrm{V}{/}^{\circ }\mathrm{C}\\ =-7.5\times {10}^{-4}\mathrm{V}{/}^{\circ }\mathrm{C}\end{array}$

Substitute the electrode potential of localid="1647525882218" $3.5M$ calomel electrode at ${15}^{\circ }C$and localid="1648539294982" ${35}^{\circ }C$ in equation (1).

Temperature coefficient
=$\frac{(0.246-0.254)V}{{35}^{0}C-{15}^{0}C}$

= $$\begin{gathered} =-\frac{0.008}{20}\mathrm{V}/{}^{\circ }\mathrm{C} \\ =-4.0\times {10}^{-4}\mathrm{V}/{}^{\circ }\mathrm{C} \end{gathered}$$