sir/ madam , can you please help me solving this question:- Question:-Mercury stands at a height of 76 cm of in a barometer tube of length 86 cm and of cross section 1 cm^2 . some air leaks into the tube and the mercury column now is 67cm long . Find the volume of atmostpheric air entered into the tube

Asked by Bharadwaj.R.S | 6th Aug, 2010, 12:00: AM

Expert Answer:

When the air leaks into the barometer, it manages to push down the mercury by 76 - 67 = 9 cm, hence the pressure it exerts is (13800)(10)(0.09) = 12420 Pa.
Now PV = nRT
V = cross section x height = 1 x (86 - 67) = 19 cm3 = 19 x 10-6 m3
T = 298 K      .. room temperature
(12420)(19x10-6) = n(8.314)(298)
n = 95.25 x 10-6 mol of air enters into the barometer.
and using air density, 1.2 kg/m3 = 1.2/29 kmol/m3 = 1200/29 mol/m3      .. since molecular mass of air is 29.
Now the air volume is
95.25 x 10-6 mol/(1200/29 mol/m3 ) = 2.30 x 10-6 m3
= 2.30 cm3.
Hence 2.30 cm3 of atmospheric air enters into the tube.
Regards,
Team,
TopperLearning.

Answered by  | 6th Aug, 2010, 10:11: PM

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