Question

Calculate the number of moles of hydrogen contained in `18` litres of a gas at `27^(@)C` and `0.92` bar pressure. If the mass of hydrogen is found to be `1.350g`. Calculate the molecular mass of hydogen.

Answer 1

Correct Answer - `2.015 g mol^(-1)`
According to ideal gas equation ,
`PV = nRT ` or `n = (PV)/(RT)`
`V = 18 L , P = 0.92 "bar" , T = 27 + 273 = 300 K , R = 0.083 L "bar" K^(-1) mol^(-1)`
`:. N = ((0.92 "bar") xx (18 L))/((0.083 L "bar" K^(-1) mol^(-1)) xx (300 K)) = 0.67 mol`
Molecular mass of `H_(2)(M) = ("Mass of" H_(2))/("No. of moles of"H_(2)) = ((1.350 g))/((0.67 mol)) = 2.01 5 g mol^(-1)`