Thermodynamics and direction of change. Natural gas is primarily methane, CH4, a

Question

Thermodynamics and direction of change. Natural gas is primarily methane, CH4, and is used to heat homes. A typical home is approximately 2000 ft^2 and the ceilings are 8ft high. How many grams of methane are required to raise the temperature in home from 40 degree F to 70 degree F? How many grams of CO2 does this reaction produce? The following data may be helpful: The heat capacity of air is 1.01 J/g.K and the enthalpy of combustion of methane is -890.8 kJ/mol. Assume that the molecular weight of air is the same as nitrogen, its major component.

Explanation / Answer

We WILL need the volume of the house to calculate the amount of air in the room...

A= 2000 ft2

h = 8 ft

V= A*H = 2000 ft2 * 8 ft = 16,000 ft3 of air

a) How many grams of CH4 are needed?

Lets calculate the heat needed to increase that temperature:

Qair = m*Cp*?T

?T= Tf-Ti= 70-40 f= 30 F = 30/1.8 = 16.6

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