Question

540 calories of heat convert 1 cubic centimeter of water at ${100}^{\circ }C$ into 1671 cubic centimeter of steam at ${100}^{\circ }C$ at a pressure of one atmosphere. Then the work done against the atmospheric pressure is nearly

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

Answer 1

The correct option is B 40 cal

Amount of heat given $=540calories$
Change in volume $△V={1670}_{c.c}$
Atmospheric pressure $P=1.01\times {10}^{6}dyne/c{m}^2$
Work done against atmospheric pressure
$W=P△V=\frac{1.01\times {10}^{-6}\times 1670}{4.2\times {10}^{-7}}\approx 40cal$