A certain mass of gas occupied 850 ml at a pressure of 760 mm of Hg. On increasing the pressure it was found that the volume of the gas was 75% of it's initial value. Assuming constant temperature, find the final pressure of the gas?

V₁ = Initial volume of the gas = 850 ml
P₁ = Initial pressure of the gas = 760 mm of Hg

V₂ (Final volume) = 75% of initial 850 ml = $\dfrac{75}{100}$ of 850 atm. = $\dfrac{3 \times 850}{4}$
P₂ = Final pressure of the gas = ?

By Boyle's Law:

$\text{P}$1 \text{V}1 = \text{P}2 \text{V}2

Substituting the values :

$760 \times 850 = \dfrac{\text{P}$2 \times 3 \times 850}{4} \\[1em] \text{P}2 = \dfrac{760 \times 4}{3} \\[1em] \text{P}_2 = 1013.33 \text{ mm of Hg}

Therefore, final pressure of the gas = 1013.33 mm of Hg.