Question

A sample of $0.1\,g$ of water at $100^{\circ}C$ and normal pressure $(1.013 \times 10^5 \, Nm^{ -2})$ requires $54\,cal$ of heat energy to convert to steam at $100^{\circ}C$. If the volume of the steam produced is $167.1\, cc$, the change in internal energy of the sample, is

• A. 84.5 J
• B. 104.3 J
• C. 42.2 J
• D. 208.7 J

Answer 1

Answer: (D)

208.7 J

Answer 2

$\Delta Q = \Delta U + \Delta W$
$\Rightarrow 54 \times4.18 = \Delta U + 1.013 \times10^{5} \left(167.1 \times10^{-6} - 0\right)$
$\Rightarrow \Delta U = 208.7\, J$