Question

Benzene, an organic solvent, has the empirical formula CH. If the molar mass of benzene is 78.11 g/mol, what is the molecular formula of benzene?

Answer 1

The molecular formula of benzene is C₆H₆

Step-by-step explanation:

Empirical formula of benzene: C₁H₁

Atomic mass of carbon (C) = 12.01 g/mol

Atomic mass of hydrogen (H) = 12.01 g/mol

Therefore, Empirical formula mass of C₁H₁ = 1 × Atomic mass of C + 1 × Atomic mass of H = 12.01 + 1.008 = 13.018 g/mol

The given molar mass of benzene = 78.11 g/mol

Since, Molar mass = n × (Empirical formula mass)

Therefore, n = (Molar mass) ÷ (Empirical formula mass)

n = (78.11 g/mol) ÷ (13.018 g/mol) ≅ 6

Since, Molecular formula = (Empirical formula)ₙ

Therefore, Molecular formula of benzene = (C₁H₁)₆ = C₆H₆

Answer 2

Step-by-step explanation:

Molecular formula defined as the chemical formula which shows actual number of atoms of each element present in the compound.

Molecular formula =
`Empirical formula * n`

where, n = 1, 2, 3,.....

On the other hand, empirical formula is the simplest chemical formula which shows the whole number of atoms of each element present in the compound.

Formula to calculate empirical mass of CH is as follows.

Empirical mass = 1 × atomic mass of C + 1 × atomic mass of H

= 1 × (12.01 amu) + 1 × (1.008 amu)

= 13.018 amu

Hence, value of n will be calculated as follows.

n =
`\frac{\text{molecular mass}}{\text{empirical mass}}`

=
`(78.11 g/mol)/(13.018 g)`

= 6

Thus, we can conclude that molecular formula of benzene is
`C_(6)H_(6)`.