Question

Two moles of ideal monoatomic gas are allowed to expand adiabatically and reversibly from $300K$ and $200K$. The work done in the system is:

$(C_v=12.5J/K/mole)$

• A. $-12.5kJ$
• B. $-2.5kJ$
• C. $-625kJ$
• D. $500kJ$

Answer 1

The correct option is B $-2.5kJ$

For an adiabatic process-

$\Delta E=q+W$

As $q=0$,

$\Delta T$ =$200-300$ $=-100$

So the Work done $=n{C}_v\Delta T=2\times 12.5\times (-100)=-2500J$

W $=$ $-2.5kJ$