Thermodynamics Question 1
Question 1 - 24 January - Shift 1
$1 g$ 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 :
(1) $4320 J$
(2) $432000 J$
(3) $4800 J$
(4) $4.32 \times 10^{8} J$
Show Answer
Answer: (1)
Solution:
Formula: Work done in isobaric process
Work done $=P \Delta V$
$ \begin{aligned} & =3 \times 10^{5} \times 1600 \times 10^{-6} \\ & =480 J \end{aligned} $
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 $=0.9 \times 4800=4320 J$
