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Question

Thermodynamics~~~~~~~~~he...
c2h4 + 3o2 --> 2co2 + 2h20 delta H= -1322.9kj
delta c2h4=51.3kj/mol
delta h20= -241.8kj/mol

a) calculate the heat of formation of co2
b)how much heat will be evovled when 140g c2h4 is consumed?
c) how many moles of c2h4 will berequired to produced 2,3000 kj of heat?
d)if the molar volume of c2h4 is 22.4 liter/mol how many liters of c2h4 are required in part c?

Answer 1

a.) To answer this, you should know the base formula:
ΔH = ΔHf (products) - ΔHf (reactants)
where ΔHf = Heat of Formation.

Each ΔHf must be multiplied by the # of moles of each compound that are in the formula. Monotomic compounds (i.e. O2) are ignored. So:

ΔH = 2 ΔHf (H2O) + 2 ΔHf (CO2) - ΔHf (C2H4)

-1322.9kJ = 2 * -241.8kJ/mol + 2 * ΔHf (CO2) - 51.3kJ/mol
-1322.9kJ + 2 * 241.8kJ/mol + 51.3kJ/mol = 2 * ΔHf (CO2)
2 ΔHf (CO2) = -788
ΔHf (CO2) = -394 kJ/mol

b.) To answer this, you need to divide the mass of C2H4 by the molar mass.
Molar mass = 2 C (12) + 4 H (1) = 28 g/mol
140 g / 28 g/mol = 5 mol

Now, take the # of moles of C2H4, divided by the # of moles of C2H4 in the equation, and multiply by ΔH:
5 mol / 1 mol * -1322.9kJ = -6614.5 kJ.

c.) Divide the amount of heat released by ΔH, multiplied by the # of moles of C2H4 in the equation.
23,000 kJ / 1322.9kJ * 1 = 17.386 moles

d.) volume = 22.4 L /mol * 17.386 moles = 389 L