What are the answers to these Enthalpy questions? I need to check my them homework please

Question

1.H2O(l) H2O(g)
2.2 SO2 (g) + O2 (g) 2 SO3 (g)
3.SO3 (g) + H2O(l) H2SO4 (l)
4.2 HI(g) H2 (g) + I2 (s)
5.4 NH3 (g) + 5 O2 (g) 4 NO(g) + 6 H2O(l)
6.CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O(g)
7.CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O(l)
8.C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O(g)
9.2 Al(s) + Fe2O3 (s) Al2O3 (s) + 2 Fe(s) where ΔHf for Fe2O3 (s) = -823 kJ/mol

Answer 1

Hello Ayo

 

For each of your 9 reactions, you need to provide the ΔH°_f for each compound.  Your text book should list all these values.  In general, to solve for ΔH° of a reaction, the equation is:

 

ΔH°_rxn = ∑nΔH°_products − ∑nΔH°_reactants

 

where n is the coefficients from the balanced chemical reaction.

 

I will solve reaction #2 from your list so that you get an idea on how to perform the calculations.  You can then solve the others using a similar process.

 

2SO₂ (g) + O₂ (g) → 2SO₃ (g)

 

ΔH°_f for SO₂ = −296.1 kJ/mol

ΔH°_f for O₂ = 0 kJ/mol

ΔH°_f for SO₃ = −395.2 kJ/mol

 

ΔH°_rxn = ∑nΔH°_products − ∑nΔH°_reactants

 

            = (2 mol x −395.2 kJ/mol) − [(2 mol x −296.1 kJ/mol) + (1 mol x 0 kJ/mol)]

 

            = −790.4 kJ − (−592.2 kJ + 0 kJ)

 

            = −790.4 kJ + 592.2 kJ = −198.2 kJ