Question

A compound was found to have 78.2% Boron and 21.8% hydrogen.Its molecular mass was found to be a 27.6 g/mol.What is the molecular formula of the compound?

Answer 1

Answer:

Element

Mass (g)

78.2 21.8

Moles

78.2/10.8 21.8/1

(moles mass/molar mass of atoms of the

element)

Ratio 7.24

Divide by 7.24/7.24 21.8/7.24

(this makes the number of atoms of the

smallest one = 1)

Approx

Approx 3

Empirical (simplest) formula = BH3

smallest 3.01

This has a formula mass of 10.8 +1 x 3 = 13.8 So the molecular formula is 27.6/13.8 = 2.0 times bigger than the empirical formula So molecular formula is B2H6