A fixed volume of a gas occupies 760 cm³ at 27°C and 70 cm of Hg. What will be it's vol. at s.t.p.

Using gas laws:

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

Substituting the values:

$\dfrac{70 \times 760}{300}$ = $\dfrac{76 \times {\text{V}_2}}{273}$

Therefore:

$\text{V}_2 =\dfrac{70 \times 760 \times 273}{300 \times 76} = 637 \text{cm}^3$

Therefore, the volume occupied by the gas is 637 cm³.