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Plots of log K vs 1/T shows an intercept...

Plots of log K vs `1/T` shows an intercept of 2 on y-axis with a slope of `45^@` for studied reaction. Which of the following are correct assuming `DeltaH^@ and DeltaS^@` are temperature independent

A

`DeltaS^@ =4.606 cal`

B

`DeltaH^@ =4.606 cal`

C

`DeltaG^@=-2.75 kcal`

D

`K=100.8`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we will follow these steps: ### Step 1: Understand the relationship between K, ΔG°, ΔH°, and ΔS° The Gibbs free energy change (ΔG°) is related to the equilibrium constant (K) by the equation: \[ \Delta G^\circ = -RT \ln K \] where R is the universal gas constant (8.314 J/mol·K or 1.987 cal/mol·K). ### Step 2: Use the slope and intercept from the plot The plot of log K versus \( \frac{1}{T} \) gives us: - Slope = \(-\frac{\Delta H^\circ}{2.303R}\) - Intercept = \(\frac{\Delta S^\circ}{2.303R}\) Given: - Slope = 45° (which is equal to 1 in terms of the tangent) - Intercept = 2 ### Step 3: Calculate ΔH° From the slope: \[ -\frac{\Delta H^\circ}{2.303R} = 1 \] Rearranging gives: \[ \Delta H^\circ = -2.303R \] Using R = 2 cal/mol·K: \[ \Delta H^\circ = -2.303 \times 2 = -4.606 \text{ cal} \] ### Step 4: Calculate ΔS° From the intercept: \[ \frac{\Delta S^\circ}{2.303R} = 2 \] Rearranging gives: \[ \Delta S^\circ = 2 \times 2.303R \] Substituting R = 2 cal/mol·K: \[ \Delta S^\circ = 2 \times 2.303 \times 2 = 9.212 \text{ cal} \] ### Step 5: Calculate ΔG° Using the relationship: \[ \Delta G^\circ = \Delta H^\circ - T\Delta S^\circ \] Assuming T = 298 K: \[ \Delta G^\circ = -4.606 - 298 \times 9.212 \] Calculating: \[ \Delta G^\circ = -4.606 - 2743.776 = -2748.382 \text{ cal} = -2.748 \text{ kcal} \] ### Step 6: Calculate K Using the equation: \[ \Delta G^\circ = -RT \ln K \] Rearranging gives: \[ K = e^{-\frac{\Delta G^\circ}{RT}} \] Substituting ΔG° = -2.748 kcal (or -2748.382 cal), R = 2 cal/mol·K, and T = 298 K: \[ K = e^{\frac{2748.382}{2 \times 298}} = e^{4.607} \approx 100.8 \] ### Conclusion Now we can summarize the findings: - ΔS° = 9.212 cal - ΔH° = -4.606 cal - ΔG° = -2.748 kcal - K = 100.8 ### Final Answers 1. ΔS° is 9.212 cal (not 4.606 cal). 2. ΔH° is -4.606 cal (not 4.606 cal). 3. ΔG° is -2.748 kcal (correct). 4. K value is 100.8 (correct).

To solve the problem, we will follow these steps: ### Step 1: Understand the relationship between K, ΔG°, ΔH°, and ΔS° The Gibbs free energy change (ΔG°) is related to the equilibrium constant (K) by the equation: \[ \Delta G^\circ = -RT \ln K \] where R is the universal gas constant (8.314 J/mol·K or 1.987 cal/mol·K). ...
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