To calculate the standard Gibbs free energy of the reaction, you need to use the equation ΔG° = ΔH° - TΔS°. You already have the value of ΔH°, which is -21.83 kcal. To calculate ΔS°, you need to use the equations given to you and the equation ΔS° = ΔS°products - ΔS°reactants.
For the reaction CCl4(ℓ) + H2(g) → HCl(g) + CHCl3(ℓ), the ΔS°products is the sum of the ΔS° of the products, which is 2.398 cal K-1 + -48.71 cal K-1 = -46.312 cal K-1. The ΔS°reactants is the sum of the ΔS° of the reactants, which is -56.23 cal K-1. Therefore, ΔS° = -46.312 cal K-1 - (-56.23 cal K-1) = 9.918 cal K-1.
Now that you have all the values, you can calculate the standard Gibbs free energy of the reaction. ΔG° = -21.83 kcal - (25°C)(9.918 cal K-1) = -21.83 kcal - 247.95 cal = -269.78 kcal.
Determine ∆G° (in kcal) for the reaction
CCl4(ℓ) + H2(g) HCl(g) + CHCl3(ℓ)
at 25 °C under standard conditions. The following information is available:
At 25 °C
C(graphite) + 2Cl2(g) CCl4(ℓ) ∆S° = -56.23 cal K-1
C(graphite) + Cl2(g) + H2(g) CHCl3(ℓ)
∆S° = -48.71 cal K-1
H2(g) + Cl2(g) HCl(g) ∆S° = 2.398 cal K-1
CCl4(ℓ) + H2(g) HCl(g) + CHCl3(ℓ) ∆H° = -21.83 kcal
In class, we learned that deltaG standard=deltaH-TdeltaS. I have T and deltaH, but how do I calculate deltaS from all these equations? How do I start this problem?
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