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A free expansion of a gas results into n...

A free expansion of a gas results into no work. Explain.

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(1) When a gas expands against an external pressure `P_("ex"),` changing the volume from `V_(1)` to `V_(2)`, the work obtained is given by `W=-P_("ex")(V_(2)-V_(1))`.
(2) Hence the work is performed by the system when it experiences the opposing force or pressure.
(3) Greater the opposing force, more is the work.
(4) In free expansion, the gas expands in vaccum where it does not experience opposing force, `(P=0)`. Since external pressure is zero, no work is obtained.
`therefore W=-P_("ex")(V_(2)-V_(1))`
`=-0xx(V_(2)-V_(1))`
`=0`
(5) Since during expansion in vacuum no energy is expended, it is called free expansion.
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