Q. $1\ cm^{3}$ of water at its boiling point absorbs 540 cal of heat to become steam with a volume $= 1.013 \times 10^{5}Nm^{- 2}$ and the mechanical equivalent of heat $= 4.19\ Jcal^{- 1}$ , the energy spend in this process in overcoming intermolecular forces is

A) 540 cal
B) 40 cal
C) 500 cal
D) Zero
Explanation

(c) $dU = dQ - dW = mL - p(dV)$
$= 1 \times 540 - \frac{1.013 \times 10^{5}(1671 - 1)10^{- 6}}{4.2}$
$= 540 - 40 = 500$ cal

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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