Question

1)

Calculate the change in enthalpy (in kJ) for the reaction using the Enthalpy tables in
the back of your book.
CaCO3(s)  CaO(s) + CO2(g)

2)

5. The combustion of ethane, C2H4, is an exothermic reaction.
C2H4(g) + 3 O2(g)  2 CO2(g) + 2 H2O(l) ∆H = -1.39 x 103
J
Calculate the amount of heat liberated when 4.79 g of C2H4 reacts with excess oxygen.

Answer 1

1)

we have:

Hof(CaCO3(s)) = -1206.92 KJ/mol

Hof(CaO(s)) = -635.09 KJ/mol

Hof(CO2(g)) = -393.509 KJ/mol

we have the Balanced chemical equation as:

CaCO3(s) ---> CaO(s) + CO2(g)

deltaHo rxn = 1*Hof(CaO(s)) + 1*Hof(CO2(g)) - 1*Hof( CaCO3(s))

deltaHo rxn = 1*Hof(CaO(s)) + 1*Hof(CO2(g)) - 1*Hof( CaCO3(s))

deltaHo rxn = 1*(-635.09) + 1*(-393.509) - 1*(-1206.92)

deltaHo rxn = 178.3 KJ

Answer: 178.3 KJ

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