Question

Butane is a common fuel used in cigarette lighters and camping stoves. Normally supplied in metal containers under pressure, the fuel exists as a mixture of liquid and gas, so high temperatures may cause the container to explode. At 25.0

°

C, the vapor pressure of butane is 2.30 atm. What is the pressure in the container at 128.0

°

C? (

?

H

°

_vap = 24.3 kJ/mol.)

Answer 1

The question can be solved using Clausius-Clapeyron equation:

ln(p₂/p₁) = ( $\Delta$ H_vap/R) x [(1/T₁)- (1/T₂)]

   $\Delta$ H vap = 24.3 kj/mol, R = 8.314 jk^-1mol^-1, T₁ = 25 ⁰C = 298 k, T₂ = 128 ⁰C = 401 k, p₁ = 2.3 atm

Putting the above values in the equation we have

ln(p₂/2.3) = (24.4 X 10³/8.314) X [ (1/298) - (1/401) ]

p₂ = 28.55 atm

Thus pressure of the container at 128 0C is 28.55 atm.