The reading of a barometer decreases from 75 cmHg to 65 cmHg when some air is introduced in the vaccum space of the tube.Initial length of the space was 6 cm.IF the area of cross section of the tube is `1 cm^2` What is the volume of this air at standard pressure?

Explanation

Standard pressure means `p_1=75 cmHg`. The volume of air at that pressure =`v_1 cm^3`.
Pressure of confined air `p_2=75-65 =10 cm Hg`
Volume of confined air
`V_2={6+(75-65)} times 1=16 cm^3`
Using Boyle.s law, `p_1V_1=p_2V_2`
or, `V_1=(p_2V_2)/p_1=(10times16)/76=2.105`
So the confined air occupis a volume of `2.105 cm^3` at standard pressure.