Question

$1c{m}^3$ of water at its boiling point absorbs 540 calories of heat to become steam with a volume of $1671c{m}^3.$ If the atmospheric pressure is $1.013\times {10}^{5}N/m^2$ and the mechanical equivalent of heat = 4.19 J/calorie, the energy spent in this process in overcoming intermolecular forces is

• A. 540 calorie
• B. 40 calorie
• C. 500 calorie
• D. Zero

Answer 1

The correct option is C 500 calorie

Energy spent in overcoming inter molecular forces $\Delta U=\Delta Q-\Delta W$
$=\Delta Q-P(V_2-V_1)=540-\frac{1.013\times {10}^5(1671-1)\times {10}^{-6}}{4.2}\approx 500$ calorie