Question

During isothermal expansion of two moles of an ideal gas from 20 atm to 4 atm at 373 K, the work done is:

• A. –2.4 $kcal$
• B. 3.8 $kcal$
• C. 2.4 $kcal$
• D. –10.5 $kcal$

Answer 1

The correct option is A –2.4 $kcal$

Work done in a reversible isothermal process of gas (w) = $-2.303\times nRTlog\frac{P_1}{P_2}$

where, n is the number of moles,
R is the gas constant ($2cal/mol.K$)
T is temperature and
$P_1$ and $P_2$ are the initial and final pressure of the gas.

According to the given conditions,
$w=-2.303\times 2\times 2\times 373log\frac{20}{4}$
$=–2401.7cal$
or $-2.4kcal$