For the adsorption of hydrogen on platinum, the activation energy is $30 ~\mathrm{k} ~\mathrm{J} \mathrm{mol}^{-1}$ and for the adsorption of hydrogen on nickel, the activation energy is $41.4 ~\mathrm{k} ~\mathrm{J} \mathrm{mol}^{-1}$. The logarithm of the ratio of the rates of chemisorption on equal areas of the metals at $300 \mathrm{~K}$ is __________ (Nearest integer)
Solution
<p><strong>Step 1: Identify Activation Energies</strong></p>
<ul>
<li>Activation energy for platinum: $E_{a1} = 30 \, \mathrm{kJ/mol} = 30 \times 10^3 \, \mathrm{J/mol}$</li>
<li>Activation energy for nickel: $E_{a2} = 41.4 \, \mathrm{kJ/mol} = 41.4 \times 10^3 \, \mathrm{J/mol}$</li>
</ul>
<p><strong>Step 2: Given Constants</strong></p>
<ul>
<li>Gas constant: $R = 8.3 \, \mathrm{J} \, \mathrm{K}^{-1} \mathrm{mol}^{-1}$</li>
<li>Temperature: $T = 300 \, \mathrm{K}$</li>
<li>$\ln 10 = 2.3$</li>
</ul>
<p><strong>Step 3: Calculate Ratio of Rate Constants</strong>
<br/><br/>Using the Arrhenius equation, the ratio of the rate constants can be calculated as:
<br/><br/>$ \frac{K_2}{K_1} = \exp\left(\frac{E_{a1} - E_{a2}}{RT}\right) $</p>
<p><strong>Step 4: Find Logarithm of the Ratio</strong><br/><br/>
Taking the natural logarithm and using $\ln 10 = 2.3$ to convert to base-10 logarithm:
<br/><br/>$ \log \frac{K_2}{K_1} = \frac{\ln\left(\frac{K_2}{K_1}\right)}{\ln 10} = \frac{E_{a1} - E_{a2}}{2.3 \cdot RT} $</p>
<p><strong>Step 5: Substitute Values</strong>
<br/><br/>$ \log \frac{K_2}{K_1} = \frac{(30 \times 10^3 - 41.4 \times 10^3) \, \mathrm{J/mol}}{2.3 \times 8.3 \, \mathrm{J} \, \mathrm{K}^{-1} \mathrm{mol}^{-1} \times 300 \, \mathrm{K}} \approx 1.99 $</p>
<p><strong>Step 6: Final Answer</strong>
<br/><br/>The nearest integer to the calculated value is 2.</p>
<p>So, the logarithm of the ratio of the rates of chemisorption on equal areas of platinum and nickel at 300 K is 2.</p>
About this question
Subject: Chemistry · Chapter: Surface Chemistry · Topic: Adsorption
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