A gas is enclosed in a vessel of volume 1000 cc at a pressure of 72.6 cm of Hg. It is being evacuated with the help of a piston pump, which expels 10% gas in each stroke. The pressure after the second stroke will be nearest to
A
60 cm
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B
55 cm
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C
66 cm
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D
50 cm
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Solution
The correct option is A 60 cm Since 10% of gas is expelled after each stroke, and PV = constant (assumption for the process) The pressure also reduces by 10%. Initial pressure is 72.6cm of Hg. After one stroke, 90% of 72.6cm = 65.34cm of Hg After second stroke, 90% of 65.34cm = 58.8cm of Hg Which is closest to 60cm of Hg. Option A is correct.