Question

An unknown gas shows a density of 3 g per litre at 273°C and 1140 mm Hg pressure. What is the gram molecular mass of this gas?

Answer 1

Given:

P₁ = 1140                             

P₂ = 760 mm

V₁ = 1000 cc                       

V₂ = ?

T₁ = 273 + 273 = 546 k       

T₂ = 273 k

`(P_1 V_1)/T_1 = (P_2 V_2)/T_2`

`V_2 = (P_1 V_1 T_2)/(T_1 P_2)`

= `(273 xx 1140 xx 1000)/(546 xx 760)`

∴ V₂ = 750 cc

750 cc at STP weighs = 3 g

∴ 224000 cc at STP weighs = `(3 xx 22400)/750`

= 89.6 g

∴ Mol. mass of gas = 89.6 g