JEE MAIN - Chemistry (2024 - 1st February Evening Shift - No. 25)
(Given $\mathrm{R}=8.314 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}$ )
Explanation
To determine the change in standard Gibbs free energy ($\Delta G^{\circ}$) for the reaction at a given temperature when the equilibrium constant ($K$) is known, we can use the following relationship:
$$ \Delta G^{\circ} = -RT \ln K $$
Here, $R$ is the universal gas constant ($8.314 \ J K^{-1} mol^{-1}$), $T$ is the temperature in Kelvin ($300 \ K$), and $K$ is the equilibrium constant.
Puting the values we get,
$$ \Delta G^{\circ} = -8.314 \times 300 \times \ln(10) $$
We can convert the natural logarithm of 10 to base-10 logarithm, using the change of base formula, $\ln(10) = 2.3026$. So,
$$ \Delta G^{\circ} = -8.314 \times 300 \times 2.3026 $$
Calculating this yields:
$$ \Delta G^{\circ} = -8.314 \times 300 \times 2.3026 = -5743.914 \ J mol^{-1} $$
To convert this to kilojoules per mole, we divide by 1000:
$$ \Delta G^{\circ} = -5.743914 \times 10^{3} \ J mol^{-1} \times \frac{1 \ kJ}{10^{3} J} = -5.743914 \ kJ mol^{-1} $$
Now, when expressing this in terms of $\times 10^{-1} \ kJ mol^{-1}$, we get:
$$ \Delta G^{\circ} = -57.43914 \times 10^{-1} \ kJ mol^{-1} $$
Therefore, $\Delta G^{\circ}$ for the reaction is approximately $-57.43914 \times 10^{-1} \ kJ mol^{-1}$ or $-57.4 \times 10^{-1} \ kJ mol^{-1}$ when rounded to three significant figures.
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