Question

A gas occupied a volume of 250 ml at 700 mm Hg pressure and $25 ^ { \circ } \mathrm { C }$ . What additional pressure is required to reduce the gas volume to its 4/5^th value at the same temperature

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

Answer 1

Answer: (B)

175 mm Hg

Answer 2

$P _ { 1 } V _ { 1 } = P _ { 2 } V _ { 2 }$

$700 \times 250 = P _ { 2 } \times \left( \frac { 4 } { 5 } \times 250 \right)$ ; $P _ { 2 } = 875 \mathrm {~mm} \mathrm { Hg }$

Additional pressure required = 875 – 700 = 175 mm Hg