Question

7. The formulas weight for isobutylene is 57. Isobutylene is raw material for making synthetic rubber A sample with a mass of 0.6481 g was found to contain 0.5555 g of carbon; the rest was hydrogen. What are the empirical and molecular formulas of this compound?

Answer 1

Empirical formula = C₁H₂

Molecular formula = C₄H₈

Step-by-step explanation

Given:

Total mass of sample = 0.6481 g

Mass of C = 0.5555 g

Mass of H = (0.64881 - 0.5555) g = 0.0926 g

Formula weight = 57

What to find:

The empirical and molecular formulas of the compound.

Step-by-step solution:

Step 1: Divide the mass of each element by their atomic mass:

Mole of C = 0.5555g/12.01 g/mol = 0.0463 mol

Mole of H = 0.0926 g/1.008 g/mol = 0.0919 mol

Step 2: Divide each mole by the smallest mole (mole ratio).

C = 0.0463/0.0463 = 1

H = 0.0919/0.0463 = 2

Step 3: Write the Empirical formula of the compound using the mole ratio in step 2.

Empirical formula = C₁H₂

Step 4: Determine the molecular formula of the compound using the empirical formula and the formula weight.

(Molecular formula) = (Empirical formula)ₙ

(57) = (C₁H₂)ₙ

57 = (1 x 12.01 + 2 x 1.008)ₙ

57 = (12.01 + 2.016)ₙ

57 = (14.026)ₙ

n = 57/14.026

n = 4

Molecular formula = (C₁H₂)₄ = C₄H₈

Therefore, the molecular formula = C₄H₈