Answer to Question #147295 in Inorganic Chemistry for shapopi phellep

Question

Given the following data:

2 H2 (g) + C (s) → CH4 (g) ΔG° = -51 kJ

2 H2 (g) + O2 (g) → 2H2O (ℓ) ΔG° = -474 kJ

C (s) + O2 (g) → CO2 (g) ΔG° = -394 kJ

Calculate ΔG° for CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (ℓ).

Answer 1

Using hess law

To find the change in G for the reaction, we must make sure the 3 equations results to the 4th equation by manipulating the coefficients and changing the reaction from product to reactant or vice versa.

For the first equation since CH4 is found in reactant side for the 4th reaction so we change CH4 to the reactant side which changes the change in its G to positive

So we have

CH4--------2H2+C

As for the 2nd and 3rd equation, they remain as they are since thats how they are seen in the 4th equation

So writing all the equations we have;

CH4---------2H2 + C +51KJ

2H2 + O2--------2H2O -474KJ

C + O2---------CO2 -394KJ

If 2H2 cancels out and C also cancels out,Adding all the equations together we have;

CH4 + 2O2 ----------2H2O + CO2

To calculate the change in G we add all the dG together

[phone]=-817KJ