Question

$1 \,g$ of a liquid is converted to vapour at $3 \times 10^5 Pa$ pressure. If $10 \%$ of the heat supplied is used for increasing the volume by $1600 \, cm ^3$ during this phase change, then the increase in internal energy in the process will be:

• A. $4800 \, J$
• B. $4320 \, J$
• C. $4.32 \times 10^8 \, J$
• D. $432000 \, J$

Answer 1

Answer: (B)

Work done $= P \Delta V$
$=3 \times 10^5 \times 1600 \times 10^{-6}$
$=480 J$
Only $10 \%$ of heat is used in work done.
Hence $\Delta Q=4800 J$
The rest goes in internal energy, which is $90 \%$ of heat.
Change in internal energy $=0.9 \times 4800=4320 J$