Question

Problem 6.29 (2)

Part A

Assuming that ΔH∘f is constant in the interval 275 K - 600. K, calculate ΔG∘ for the process (H2O, g,298→H2O, g, 597 K ).

**Delta G is in the units: J*mol^-1

Part B

Calculate the relative change in the Gibbs energy.

Express your answer using two significant figures.

**Relative change is a percentage!!

Express your answer using four significant figures.

Answer 1

Part A

Assuming that ΔH∘f is constant in the interval 275 K - 600. K, calculate ΔG∘ for the process (H2O, g,298→H2O, g, 597 K ).

**Delta G is in the units: J*mol^-1

To calculate the ΔG∘ for the process (H2O, g,298→H2O, g, 597 K ).

We use following expression:

ΔG∘f (T2) = T2 [ΔG∘ F(T1)/T1   + ΔH∘f (T1 ){1/T2-1/T1}]

= 597* [-228.6*10^3 J moles-1/298 K   - 241.8*10^3J Mole -1 {1/597 K-1/298K}]

= 597K* [-767.11 J moles-1K-1    - 241.8*10^3J Mole -1 {1.67*10^-3 K-3.35*10^-3}]

= 597 K* [-767.11 J moles-1K-1    +406.224 J moles-1K-1    ]

=-215448.9 J moles-1

= -215.45 KJ mole-1

Part B

Calculate the relative change in the Gibbs energy.

the relative change in the Gibbs energy

= 228.6*10^3 J moles -215.45 KJ mole-1 /228.6*10^3 J moles*100

= 5.75%

= 5.8%