Question

A barometer tube is 1 m long and `2cm^(2)` in cross section. Mercury stands to a height of `75cm` in the tube. When a small amount of oxygen is introduced in the space above the mercury level, the level falls by 5cm. Calculate the mass of the oxygen is introduced. Room temperature=`27^(@)C`, g=10 m s_(-2)` and density if mercury =`13600kg m^(-3)`.

Answer 1

The pressure of oxygen in the space above the mercury level=5 cm of mercury
`=0.05mxx13600kg m^(-3)xx10ms^(-2)
=6800N m^(-2).
The volume of oxygen =(2cm^(2))xx(25cm+5cm)
=60cm^(3)=6xx10^(-5) m^(-3)
The temperature =(273+27)K=300K.
The amount of oxygen is n=(pV)/(RT)
=((6800N m^(-2))xx6xx10^(-5)m^(-3))/((8.3JK^(-1)mol^(-1))xx(300K)
16.4xx10^(-5)mol.
THe mass of oxygen is
(16.4xx10^(-5)mol)xx(32g mol^(-1)
`=5.24xx10^(-3) g.`