Question

540 calories of heat convert 1 cubic centimeter of water at $100^{o}C$ into 1671 cubic centimeter of steam at $100^{o}C$ 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

Answer: (B)

40 cal

Answer 2

Amount of heat given $= 540\mspace{6mu} calories$

Change in volume $\Delta V = 1670\mspace{6mu} c.c$

Atmospheric pressure

$P = 1.01 \times 10^{6}\mspace{6mu} dyne/cm^{2}$

Work done against atmospheric pressure

$W = P\Delta V = \frac{1.01 \times 10^{6} \times 1670}{4.2 \times 10^{7}} \approx 40\mspace{6mu} cal$