NEET Physics Thermodynamical Processes NEET PYQ-Thermodynamical Processes

A sample of 0.1 g of water at \[\text{100 }\!\!{}^\circ\!\!\text{ C}\]and normal pressure \[\text{(1}\text{.013 }\!\!\times\!\!\text{ 1}{{\text{0}}^{\text{5}}}\text{N}{{\text{m}}^{\text{--2}}}\text{)}\] requires 54 cal of heat energy to convert to steam at\[\text{100 }\!\!{}^\circ\!\!\text{ C}\]. If the volume of the steam produced is 167.1 cc, the change in internal energy of the sample, is                                                                                                                                              [NEET - 2018]

A) 42.2 J

B)      208.7 J

C) 104.3 J

D)      84.5 J

Correct Answer: B

Solution :

[b] \[\Delta \text{Q=}\Delta \text{U+}\Delta \text{W}\]

\[\Rightarrow 54\times 4.18=\Delta U+1.013\times {{10}^{5}}(167.1\times {{10}^{-6}}-0)\]

\[\Rightarrow \Delta U=208.7\,\,\text{J}\]