Question

A fuel-air mixture is placed in a cylinder fitted with a piston. The original volume is 0.310-L. When the mixture is ignited, gases are produced and 935 J of energy is released. To what volume will the gases expand against a constant pressure of 635 mmHg, if all the energy released is converted to work to push the piston? □ 12.8 L 114L 9.02L 10.2L

Answer 1

Answer:

$V_2=11.35L$

Explanation:

Knowing that the system is at constant pressure, the energy balance is:

$\Delta H=Q-W$

If all the energy (enthalpy of combustion) is transformed into work:

$\Delta H=-W$

Work:

$W=-\int_{V1}^{V2}P*dV$

$W=-P*(V_2-V_1)$

$\Delta H=P*(V_2-V_1)$

Calculating:

$935J=84659 Pa*(V_2-3.1*10^{-4}m^3)$

$V_2=0.0113 m^3=11.35L$