1. Calculate Delta H rxn ( H rxn) for the combustion of acetylene: 2 C 2 H 2 (g)

Question

1. Calculate Delta H rxn (Hrxn) for the combustion of acetylene: 2 C2H2 (g) + 5 O2 (g) --> 4 CO2 (g) + 2 H2O (g)

2. An experimental fuel is a mixture of 83% ethanol and 17% gasoline by volume. Calculate how much energy in the form of heat is available from 100 mL of this mixture and compare it with the amount from pure gasoline. Assume the densities of ethanol and gasoline are 0.789 and 0.737 g/mL, respectively, and that n-none is an appropriate model hydrocarbon for gasoline.

Heat from experimental fuel: ________ kJ

Heat from gasoline: ________ kJ

Explanation / Answer

C2H2 (g) + 5 O2 (g) --> 4 CO2 (g) + 2 H2O (g)

So, the balanced chemical reaction is

C

C2H2(g)+5/ 2O2(g) -->2CO2(g)+H2O(g)

The enthalpy of combustion will be calculated as follows:

Hcomb=(2H0CO2+HH2O)(HC2H2)

Hcomb=[2(393.5)+(241.6)](226.7)

Hcomb=1255.3 kJ

Therefore, Delta H rxn (Hrxn) for the combustion of acetylene is

Hcomb=1253.3 kJ/mol

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