Question

7. Using Hess’ Law, what is the enthalpy of reaction, ΔH, for the formation of methane, CH4, from solid carbon and hydrogen gas?
C(s) + 2H2(g) = CH4
Use the following reactions to determine the answer:
H2(g) + 1/2 O2(g) = H2O(l) ΔHo = -393.5 KJ
C(s) + O2(g) = CO2 ΔHo = -285.8 KJ
CH4(g) + 2 O2(g) = CO2(g) + H2O(l) ΔHo = -890.3 KJ

Answer 1

$\Delta H=2\Delta H1 + \Delta H2 - \Delta H3$

$\Delta H = -182.5 kJ$