Question

The enthalpies of formation of the compounds in the combustion of methane, , are CH4 (g): Hf = –74.6 kJ/mol; CO2 (g): Hf = –393.5 kJ/mol; and H2 O(g): Hf = –241.82 kJ/mol. How much heat is released by the combustion of 2 mol of methane? Use . 80.3 kJ 802.5 kJ 1,605.1 kJ 6,420.3 kJ

Answer 1

Answer:

ΔH°c = - 1605.1 KJ

Explanation:

• CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

∴ ΔHf CH4(g) = - 74.6 KJ/mol

∴ ΔHf CO2(g) = - 393.5bKJ/mol

∴ ΔHfH2O(g) = - 241.82 KJ/mol

standard enthalpy of combustion (ΔH°c):

⇒ ΔH°c = (2)(ΔHf H2O) + ΔHfCO2 - ΔHfCH4

⇒ ΔH°c = (2)(- 241.82) + ( - 393.5 ) - ( - 74.6 )

⇒ ΔH°c = - 802.54 KJ/mol

⇒ ΔH°c = ( - 802.54 KJ/mol )(  2 mol CH4 )

⇒ ΔH°c = - 1605.08 KJ