Answer to Question #100225 in General Chemistry for Beverlie

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

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

$\Delta H = -182.5 kJ$