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For a reversible reaction A hArr B. Find...

For a reversible reaction `A hArr B`. Find `(log_(10)K)/(10)` at `2727^(@)`C temperature
Given
`Delta_(r)H^(0)` = - 54.07 kJ `mol^(-1)`
`Delta_(r)S^(0)` = 10 `JK^(-1)`
R = 8.314 `JK^(-1) mol^(-1)`

Text Solution

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The correct Answer is:
To solve the problem, we will use the relationship between the Gibbs free energy change (ΔG°), the enthalpy change (ΔH°), the entropy change (ΔS°), and the equilibrium constant (K) for the reaction. The steps are as follows: ### Step 1: Convert the temperature from Celsius to Kelvin Given the temperature is 2727°C, we convert it to Kelvin using the formula: \[ T(K) = T(°C) + 273 \] \[ T = 2727 + 273 = 3000 \, K \] **Hint:** Remember to always convert Celsius to Kelvin by adding 273. ### Step 2: Write the relationship between ΔG°, ΔH°, and ΔS° The Gibbs free energy change is related to the enthalpy and entropy changes by the equation: \[ \Delta G° = \Delta H° - T \Delta S° \] **Hint:** This equation shows how Gibbs free energy is affected by enthalpy and entropy. ### Step 3: Relate ΔG° to the equilibrium constant K The relationship between Gibbs free energy and the equilibrium constant is given by: \[ \Delta G° = -RT \ln K \] Where R is the gas constant. **Hint:** This equation connects thermodynamic properties with the equilibrium constant. ### Step 4: Equate the two expressions for ΔG° By equating the two expressions for ΔG°, we have: \[ \Delta H° - T \Delta S° = -RT \ln K \] **Hint:** This step combines the two equations to find a relationship involving K. ### Step 5: Solve for ln K Rearranging the equation gives: \[ \ln K = \frac{\Delta H° - T \Delta S°}{-RT} \] **Hint:** Isolate ln K to express it in terms of ΔH°, ΔS°, T, and R. ### Step 6: Convert ln K to log₁₀ K Using the conversion between natural logarithm and base 10 logarithm: \[ \ln K = 2.303 \log_{10} K \] Thus, \[ \log_{10} K = \frac{\ln K}{2.303} \] **Hint:** Remember the conversion factor between natural log and log base 10. ### Step 7: Substitute values into the equation Now we substitute the values into the equation: - ΔH° = -54.07 kJ/mol = -54070 J/mol (convert kJ to J) - ΔS° = 10 J/K - R = 8.314 J/K·mol - T = 3000 K So we have: \[ \log_{10} K = \frac{\Delta H° - T \Delta S°}{-RT \cdot 2.303} \] ### Step 8: Calculate log₁₀ K Substituting the values: \[ \log_{10} K = \frac{-54070 - (3000)(10)}{- (8.314)(3000) \cdot 2.303} \] \[ \log_{10} K = \frac{-54070 - 30000}{- (8.314)(3000) \cdot 2.303} \] \[ = \frac{-84070}{- (8.314)(3000) \cdot 2.303} \] Calculating the denominator: \[ = (8.314)(3000) \cdot 2.303 \approx 57440.1 \] Thus, \[ \log_{10} K \approx \frac{84070}{57440.1} \approx 1.46 \] ### Step 9: Find log₁₀ K / 10 Finally, we need to find: \[ \frac{\log_{10} K}{10} \approx \frac{1.46}{10} = 0.146 \] ### Final Answer Thus, the value of \(\frac{\log_{10} K}{10}\) at 2727°C is approximately \(0.146\). ---
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