Question

A compound contains 92.3percent of carbon nd 7.7percent of hydrogen The molecule of compound is 39 times heavier than hydrogen molecule the molecular formula of the compound is

Answer 1

percentage of carbon in compound = 92.3%

percentage of hydrogen in compound = 7.7%

find percentage atomic mass ratio

for carbon ⇒ 92.3/12 = 7.69 ≈ 7.7

for hydrogen ⇒7.7/1 = 7.1

find simple ratio of (percentage mass ratio )

so, C : H = 7.7 : 7.7 = 1 : 1

hence, empirical formula of compound is CH.

a/c to question,

the molecule of compound is 39 times heavier than hydrogen.

so, molar mass of compound = 39 × 1g/mol = 39 g/mol [ as atomic mass of hydrogen = 1g/mol ]

so, n × (mass of empirical formula) = 39

or, n × (12 + 1) = 39

or, n = 3

so, molecular formula of compound is n(CH) = 3(CH) = C3H3