Answer
See the detailed answer below.
Work Step by Step
a) Find the number of moles of a gas if you know that there is 50 J of work exerted on it that compresses its volume to one-third of its initial volume at a constant temperature of 77$^\circ$C.
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b) Solving for $n$;
$$n=\dfrac{50}{-(8.31)(355)\ln(\frac{1}{3})}$$
$$n=\color{red}{\bf -0.0154}\;\rm mol$$
