Question

Question #26832

Answer 1

-435 kcal

Explanation:

This is a problem that employs stoichiometry. Just as the molar ratios between products and reactants can be used to figure how much product is made the enthalpy change the energy released in kcal can be used as a stoichiometric value.
`(32.0g CH4)/ (16.04 g/(mol))=1.995 mols CH4`
`1.995 mols CH4 (-218 kcal)/(1mol CH4)=-434.9 kcal`
Correct rounding with sig figs is three digits since the provide numbers in the problem on have three sig figs: -435 kcal
if you are wondering why the energy is negative is becuase this reaction is exothermic and energy is released aka lost by the system into the surroundings.