Question

Consider a mixture of air and gasoline vapor in a cylinder with a piston. The original volume is 40. cm3. If the combustion of this mixture releases 912 J of energy, to what volume will the gases expand against a constant pressure of 635 torr if all the energy of combustion is converted into work to push back the piston?

Answer 1

Answer:

The gases will expand until a volume of Vf= 10812 cm^3

Explanation:

Since the gas mixture is expanding at constant pressure

$W=\int\limits^{Vf}_{Vi} {P} \, dV =P(Vf-Vi)$

and therefore

$Vf=W/P+Vi$

knowing that 1 torr=133,32 Pa

$p=635 torr * 133,322 Pa/torr * 1m^{3}/10^{6}cm^{3}=0,08466 J/ cm^{3}$

therefore

$Vf=912 J/(0,08466 J/cm^{3}) +40cm^{3} =10812 cm^{3}$