Calculate the weight of the substance if it’s molecular weight is 70 and in the gaseous form occupies 10 lits. at 27°C and 700 mm pressure.

Using the gas equation,

⇒ P_1V_1\over T_1=P_2V_2\over T_2

Substituting the values we get,

⇒ 700 × 10\over 300=760× x\over 273

⇒ x = 700 × 10 × 273\over 300 × 760

⇒ x = 1911\over 228 = 8.38 lit

∴ 70 g of the gas occupies 22.4 lit. at s.t.p.

If $y$ g of the gas occupies 8.38 lits, then

y = 70\over 22.4 ×8.38

= 26.18

Hence, weight of substance is 26.18 g