Answer to Question #122507 in Molecular Physics | Thermodynamics for Oluchi

Question

A closed system consisting of 1kg gaseous co² undergoes a reversible process at constant pressure causing a decrease of 30kj in internal energy
Determine the work done during the process
Take CP=840j/kg°c and CV=600j/kg°c

Answer 1

As per the given question,

m=1 kg

Pressure is constant.

Change in internal energy of the gas =-30kJ

Work one during the process=?

CP=840j/kg°c

CV=600j/kg°c

We know that $\Delta U= mC_v(T_1 -T_2)$

Now substituting the values,

$\Rightarrow -30000J=1\times 600(T_1 -T_2)$

$\Rightarrow (T_1 -T_2)= 50^\circ C$

The supplied heat or rejected heat,

$\Rightarrow Q=m c_p(T_2-T_1)$

$=840\times -50$

$=-42kJ$

We know that,

$Q=\Delta U+W$

$\Rightarrow W=Q-\Delta U$

$\Rightarrow W=-42kJ+30=-12kJ$