Question

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

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

Answer 1

The correct option is A q = + 208 J, W = - 208 J

The process is isothermal expansion, hence
q = - W
$\Delta E=0$
$W=-2.303nRTlog\frac{V_2}{V_1}$
$=-2.303\times 0.04\times 8.314\times 310\times log\frac{335}{50}$
$=-208J$
q = + 208 J, W = -208 J (expansion work)