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Question: Answered & Verified by Expert
A system given out $\mathrm{x} \mathrm{J}$ of heat and does $\mathrm{y} \mathrm{J}$ of work on it's surrounding. What is the internal energy change?
ChemistryThermodynamics (C)MHT CETMHT CET 2021 (23 Sep Shift 2)
Options:
  • A $-x-y ~ J$
  • B $y-x ~ J$
  • C $x-y ~ J$
  • D $x+y ~ J$
Solution:
1666 Upvotes Verified Answer
The correct answer is: $-x-y ~ J$
$\mathrm{q}=-\mathrm{xJ}$ Heat released by system $(-)$ ve $\mathrm{w}=-\mathrm{yJ}$ Work done by system $(-)$ ve From first law of thermodynamics.
$$
\begin{aligned}
& \Delta \mathrm{U}=\mathrm{q}+\mathrm{w} \\
& =-\mathrm{x}-\mathrm{y} \mathrm{J}
\end{aligned}
$$

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