A gas occupies a volume of 250 ml at 700 mm Hg pressure and `25^(@)C` . What additional pressure is required to reduces the gas volume to its `4//5` th value at the same temperature ?

Options

A. 225 mm Hg
B. 175 mm Hg
C. 150 mm Hg
D. 265 mm Hg

Answer

B

Explanation

`V_(2) = 250 ml` , `P_(1) `= 700mm Hg
`V_(2) = 250 xx ( 4)/( 5)`
`= 200 ml , P_(2) = ?`
According to Boyle.s law,
`P_(1) V_(1) = P_(2) V_(2)`
or `P_(2) = ( 250 xx 700)/( 200) = 875 mm Hg`
Additional pressure required
`= 875 - 700`
= 175 mm Hg