Answer to Question #100295 in General Chemistry for Beverlie

Question

1. 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

$$H_2+\frac{1}{2}O_2\to H_2O\ .....(1)\ -393.5kJ$$

$$C+O_2\to CO_2\ ....(2)\ -285.8\ kJ$$

$$2H_2O+ CO_2\to CH_4+ 2O_2 \ ....(3)\ 890.3\ kJ$$

$$Applying\ (2)\ +(2\times(1))\ +(3)$$

$$C+2H_2\to CH_4\ ....(4)\ -182.5\ kJ/mol$$

Hence enthaly of formation of methane is $182.5\ kJ/mol$