Question

When fuel is burned in a cylinder equipped with a piston, the volume expands from 0.245 L to 1.280 L against an external pressure of 1.02 atm . In addition, 843 J is emitted as heat. What is ΔE for the burning of the fuel?

Answer 1

Answer:

$-949.97\ \text{J}$

Explanation:

$P$ = Pressure = $1.02\ \text{atm}$

$dv$ = Change in volume = $(1.28-0.245)\ \text{L}$

$q$ = Emission of heat = $843\ \text{J}$

Work done is given by

$W=-Pdv\\\Rightarrow W=-1.02(1.28-0.245)\times 10^{-3}\times 101325\\\Rightarrow W=-106.97\ \text{J}$

Total energy of the system

$E=W+q\\\Rightarrow E=-106.97-843\\\Rightarrow E=-949.97\ \text{J}$

The $\Delta E$ for the burning of the fuel is $-949.97\ \text{J}$.