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Homework answers / question archive / Many cigarette lighters contain liquid butane, C4H10(l)
Many cigarette lighters contain liquid butane, C4H10(l). Using standard enthalpies of formation, calculate the quantity of heat, in kJ, produced when 2.0 g of butane is completely combusted in air under standard conditions.
Answer:
The standard enthalphy of formation of C4H10(l) is -125.58 KJ / mol
C4H10(l) + (13/2)O2 (g) ----> 4CO2 (g) + 5H2O (l) : ΔH = ?
ΔH = ΔH products - ΔH reactants
= 4* ΔH CO2 (g) + 5 * ΔH H2O (l) - ( ΔH C4H10(l) + (13/2) *ΔH O2 (g) )
= 4 * -393.509 KJ / mol + 5*-285.83 KJ / mol ) - ( -125.58 KJ / ml + (13/2) * 0 )
= -2877.6 KJ / mol
Molar mass of C4H10 = 4 * 12 + 10 * 1 = 58 g / mol
that is for 58 g of C4H10 the heat releseased is 2877.6 KJ
So for 2g of C4H10 the heat releseased is = (2877.6 KJ * 2 ) / 58
= 99.227 KJ