Question

Consider a mixture of air and gasoline vapor in a cylinder with a piston. The original volume is 30. cm3. If the combustion of this mixture releases 943 J of energy, to what volume will the gases expand against a constant pressure of 632 torr if all the energy of combustion is converted into work to push back the piston?

Answer 1

Original Volume = 30 cm³ = 30x10^-6 m³

P = Pressure = 632 Torr

Since 1 torr = 133.3 Pa

So, P = 632x133.3 =84245.6 Pa

w (work done) = Energy released from the combustion of mixture of air and gasoline = -943J (negative because work done by the system on the surroundings)

since the work done is given by the equation:

w = -P∆V

∆V = -w/P

V₂-V₁ = -w/P (V₂ is final volume and V₁ is initial volume)

V₂- 30x10^-6    = -(-943)/84245.6

V₂ =30x10^-6 +.0111934

= .011223m³

The gases expand to a volume of .011223m³.