a. The energy released from 5.0 mol of methane is -1065 kcal/mol.
b. The number of moles of methane needed to give 100. kcal heat is 0.4694 moles.
What is combustion?
Combustion is a chemical process in which the element reacts with oxygen to produce heat and light. Burning of wood.
The equation of combustion of methane:
CH₄ (g) + 2O₂(g) ------> CO₂ (g) + 2H₂O (l)
a) Enthalpy of the reaction is H = -213 Kcal/mol
This means 213 Kcal heat is released in the burning of one mole of CH4
H reaction = [ H products ] - [ H reactants ]
Hr = [ H(CO₂)g + 2H(H₂O)l ] - [ H(CH₄)g ] = -213 kcal/mol
For 5 moles of methane:
5CH₄(g) + 10O₂(g) -----> 5CO₂(g) + 10H₂O(l)
therefore, new Hr = 5 x -213 = -1065 kcal/mol
H reaction = -1065 kcal/mol
b) 213 kcal is released per mole of Methane
then, to release 100 kcal we need, 100 / (213) = 0.4694 moles
Thus, the energy released is -1065 kcal/mol, and the number of moles is 0.4694 moles.
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