Question

Calculate ΔHrn for the following reaction 50(s) + 6H2(g) → C5H12(1) Use the following reactions and given AH's. C5H12(1) + 802 (g) → 5CO2(g) + 6H20(g), ΔH=-3244.8 kJ C(s) + O2(g) → CO2 (g), ΔH=-393.5 kJ 2H2 (g) + O2 (g) → 2H2O(g), ΔH=-483.5 kJ Express your answer to for significant figures kJ

Answer 1

let us number the reactions as 1,2,3,4 from top to bottom

reaction 1 can be written as:

reaction 1 = 5*reaction 3 - reaction 2 + 3*reaction 4

so,

ΔH1 = 5*ΔH3 - ΔH2 + 3*ΔH4

ΔH1 = 5*(-393.5) - (-3244.8) + 3*(-483.5)

ΔH1 = - 173.2 KJ

Answer: - 173.2 KJ