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Question
300 M mol of perfect gas occupies 13 L at 320 K. Calculate the work done in joules when the gas expands-
(a) isothermally against a Constant external pressure of 0.20atm.
(b) isothermal and reversible process.
(c) into vaccum until the volume of gas is increased by 3L (R=8.314J mol-1 K-1)
Solution
(a) W = -Pext ΔV
=-0.20x3L
=-0.6L atm
=0.6x101.3
| W=-60.78J |
(b) `W=-2.303nRT log_10(V_2/V_1)`
`=-2.303xx.0.3xx8.314xxlog(16/13)`
=-2.303x0.3x8.314xlog(1.23)
=-2.303x0.3x8.314x0.0899x320
=-0.516x320
| w=-165.12J |
(c) W=-Pext ΔV
When a gas is expanded in vaccum, exteral opposing pressure is zero.
Pext=-(0)x3L
W=0
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