Question

A piston filled with $0.04$ mol of an ideal gas expands reversibly from $50.0mL$ to $375mL$ at a constant temperature of ${37.0}^{o}C$. As it does so, it absorbs $208J$ of heat. The values of $q$ and $w$ for the process will be:
($R=8.314J/mol$ $K$) ($\ln 7.5=2.01$)

• A. $q=+208J,w=-208J$
• B. $q=-208J,w=-208J$
• C. $q=-208J,w=+208J$
• D. $q=+208J,w=+208J$

Answer 1

Answer: (A)

$q=+208J,w=-208J$

Given that the heat is absorbed by the system.

Therefore,

$q=+208J$

Now, as temperature is constant, i.e., $\Delta T=0$

Therefore $\Delta U=0$

Now from first law of thermodynamics,

$\Delta U=q+w$

$\because \Delta U=0$

$\therefore w=-q=-208J$

Option A is correct.