Question

Calculate the standard molar Gibbs energy of formation of $CS_{2}$, given that its standard enthalpy of formation is 89.7 kJ $mol^{-1}$ and the standard molar entropies of graphite, S and $CS_{2}$ are 5.7, 31.8 and 151.3J$K^{-1}$$mol^{-1}$ respectively.

Answer 1

In order to calculate standard Gibbs free energy of formation of carbon disulphide, we can calculate it from the Gibbs Helmholtz equation.

According to the question, standard enthalpy of formation is given and the entropy of carbon, S, CS2 is also given.

Now, we can calculate the Gibbs free energy is as follows

∆G=∆H-T∆S: [Gibbs Helmholtz equation]

Calculating ∆S rxn =∆S products - ∆S reactants

∆G =$=89.7\times 10^{-3} -(298)(151.3-5.7-2(3.18) J$

∆G =65,264 J