Consider the reaction for the decomposition of carbon tetrachloride gas:CCl4(g) → C(s, graphite) + 2 Cl2(g) ΔH rxn = +95.7 kJ; ΔS rxn = +142.2 J/K

Consider the reaction for the decomposition of carbon tetrachloride gas:

CCl4(g) → C(s, graphite) + 2 Cl2(g) ΔH rxn = +95.7 kJ; ΔS rxn = +142.2 J/K

Calculate ΔG rxn at 25 °C and determine whether the reaction is spontaneous.

Solution:

ΔG=ΔH-TΔS

First of all we notice that the unirs for ΔH and ΔS are different. We will convert ΔH from kJ into J by multiplying by 1000. ΔH= 95.7kJ(1000J/1kJ) = 95700J. We also need to convert temperature from Celcius to K. 25°C+273= 295K Now we can plug everything into the formula. ΔG= 95700J - 295K(142.2J/K)= 53751J

Since ΔG is positive, this means the reaction is NOT spontaneous.

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