Question

A gas in a cylinder held at a constant pressure of $1.7\times {10}^5$ Pa and is cooled and compressed from $1.20m^{3}to0.8m^3$. The internal energy of the gas decreses by $1.1\times {10}^5$ J.

Does it matter whether or not the gas is ideal? Mark 1->Yes and 0->No

• A. 0

Answer 1

The correct option is A 0
The first law of thermodynamics (conservation of energy):
$\delta Q=\Delta U+w$
Here it is given that $\Delta U=-1.1\ast {10}^{5}J$
$w=\int PdV=P(V_2-V_1)$
i.e. $w=1.7\ast {10}^5(0.8-1.2)=-0.68\ast {10}^{5}J$
$\delta Q=\Delta U+w=-1.78\ast {10}^{5}J$
The first law is irrespective of whether the gas is ideal or not.