1. Determine the sign of the entropy change for the system.
Consider the combustion of propane gas: C₃H₈ (g) + 5 O₂ (g) CO₂ (g) + 4H₂O (g) ΔH rxn = kj
Calculate the entropy change in the surroundings associated with this reaction occurring at 25◦C.
Determine the sign of the entropy change for the system.
Determine the sign of the entropy change for the universe. Will the reaction be spontaneous?

2. Consider the reaction for the decomposition of carbon tetrachloride gas: CCl₄ (g) C (s, graphite) + 2Cl₂ (g) ΔH = 95.7 kJ ΔS = J/K
Calculate ΔG at 25◦C and determine whether the reaction is spontaneous or not.
If the reaction is not spontaneous at 25◦C, determine at what temperature (if any) the reaction becomes spontaneous.

3. Calculate Δ S rxn for the following balanced chemical equation
Calculate Δ S rxn for the following balanced chemical equation. 4 NH₃ (g) O₂ (g) NO (g) H₂O (g)
Use the following data for your calculations: Reactants or products S (in J/mol.K) NH₃ (g) O₂ (g) NO (g) H₂O (g) 188.8

4. Hint: use the equation ΔG rxn = ΔH rxn – TΔS rxn
One of the possible initial steps in the formation of acid rain is the oxidation of the pollutant SO₂ to SO₃ by the reaction: SO₂ (g) + ⅟2 o₂ (g) SO₃ (g) a) Calculate ΔG rxn at 25◦C and determine whether the reaction is spontaneous or not.
Hint: use the equation
ΔG rxn = ΔH rxn – TΔS rxn
b) Estimate the value of ΔG rxn at 125◦C. Is the reaction more or less spontaneous at this temperature compared to 25◦C?

5. Calculating Entropy changes in reactions when several steps of the reaction take place.
Find ΔG rxn for the reaction 3 C (s) + 4 H₂ (g) C₃H₈ (g) Use the following reactions: C₃H₈ (g) + 5 O₂ (g) 3CO₂ (g) + 4H₂O (g) kJ C (s) + O₂ (g) CO₂ (g) kJ 2 H₂ (g) + O₂ (g) 2 H₂O (g) kJ