Question

Use the data in Appendix B in the textbook to calculate ΔH∘ and ΔS∘ for each of the following reactions. From the values of ΔH∘ and ΔS∘, calculate ΔG∘ at 25 ∘C and predict whether each reaction is spontaneous under standard-state conditions.
Part A
2SO2(g)+O2(g)→2SO3(g)
Express your answer using four significant figures.

ΔH∘ =
kJ

Part B
Express your answer using four significant figures.

ΔS∘ =
  J/K

Part C
Express your answer using four significant figures.

ΔG∘ =
  kJ

Part D

spontaneous under standard-state conditions
nonspontaneous under standard-state conditions

Answer 1

enthalpy change of SO2= -296.8 Kj/mol

enthalpy change of SO3= -395.6 Kj/Mol

Enthalpy change for O2=0

Enthalpy change at standard conditions= sumof Enthalpy change of products- sum of Enthalpy change of reactants

2* enthalpy change of SO3-{ 2* enthalpy change of SO2+1* enthalpy change of Oxygen)

2,2 and 1 are stoichiometric coefficients of SO3,SO2 and O2 respectively.

=2*(-395.6)- {2*(-296.8)}=-197.6 Kj

b) entropy change data : SO3 : 256.6 J/mol.K, SO2 : 248.1 J/mol.K and O2=205.3 J/mol.K

Similar to the way entropy change is calculated by =sume of entropy changes of products- sum of entropy changes of reactants

entropy change= 2*256.6-{2*248.1+205.3)=-188.3 J/K

3. delG= delH- TdelS = -395.6-(298.15*(-188.3/1000) =-395.6 +298.15*188.3/1000=-339.458 Kj

since delG is -ve, the reaction is spontaneous at 25 deg.c