Q. 575.0( 1 Vote )
Let the length of barometer be x cm.
Let the curved surface area of barometer tube be A
Saturation vapor pressure (SVP) = 1.0 cm of mercury
In first case length of mercury column is 74cm.
Length of air above mercury = x-74
Volume of air column V1= (x-74)A
In first case atmospheric pressure is 76 cm of Hg.
Let pressure of air column be P1 in first case.
Atmospheric pressure= SVP+ P1+mercury column height
P1=1 …. (1)
In second case,
Length of mercury column is 72.10cm.
Length of air above mercury = x-72.10
Volume of air column V2= (x-72.1)A
Atmospheric pressure is 74 cm of Hg.
Let pressure of air column be P2.
Atmospheric pressure= SVP+ P2 +mercury column height
P2=0.9 …. (2)
Since temperature has not changed, we can apply Boyle’s law which states that PV=constant, if temperature is constant, for both the cases
Therefore, length of barometer tube is 91.1cm.
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