Question

A cylinder contain 0.33g of O.The same volume of an unknown gas X under similar condition of temperature and pressure weight 0.26g.The gas X is known to contain only carbon and hydrogen atom in the ratio of 1:1.Identify gas X.

Answer 1

according to Avogadro's law, under the similar condition of temperature and pressure number of mole of substance remains constant.

so, mole of Oxygen = mole of gas X

given weight of Oxygen, = 0.33g

molecular weight of Oxygen gas = 32g/mol.

so, mole of oxygen gas = 0.33/32 = 0.01

now, 0.01 = mole of gas X

or, 0.01 = weight of gas X/molecular weight of X

or, 0.01 = 0.26g/molecular weight of gas X

or, molecular weight of gas X = 0.26/0.01 = 26g/mol

a/c to question,

gas contains only carbon and hydrogen atom in the ratio of 1 : 1

so, empirical formula of gas X = CH

then molecular formula = n × CH

where n is integers.

now, molecular weight of gas X = n × (12 + 1) = 26

or, n = 2

so, chemical formula gas X = C2H2 (acetylene)