Question

Compound X, isolated from lanolin (sheep's wool fat), has the pungent aroma of dirty sweatsocks. A careful analysis showed that compound X contains 62% carbon and 10.4% hydrogen. No nitrogen or halogen was found.

a. Compute an empirical formula for compound X.

Express your answer as a condensed structural formula.

b. A molecular weight determination showed that compound X has a molecular weight of approximately 117. Find the molecular formula of compound X.

Express your answer as a condensed structural formula.

Answer 1

Given :

% of C = 62

% of H = 10.4

In this compound remaining element is oxygen.

% of O = 100- (62 + 10.4) = 27.6 %

Lets assume the total mass =100 g

So ,

Mass of C = 62 g

Mass of H = 10.4 g

Mass of O = 27.6 g

Lets calculate moles of each elements.

Moles of C = 62 g / 12 g per mol = 5.17 mol C

Mol H = 10.4 g / 1.008 g per mol = 10.32 mol H

Mol O = 27.6 g / 16 g per mol = 1.73 mol O

Now we find simplest ratio by dividing all the moles by smallest mol

Number of C = 5.17 / 1.73 = 2.99 = 3

Number of H = 10.32/1.73=5.96=6

Number of O = 1.73/173 = 1

Empirical formula = C3H6O

b)

Determined molecular weight = 117

To find molecular formula we need its empirical formula mass

Empirical formula mass = C3 H6 O = 12 * 3 + 1.008 * 6 + 16 * 1 = 58.079

Molecular formula = n * (empirical formula)

n = molecular formula mass/ empirical formula mass

= 117 / 58.079 = 2.01

= 2

Molecular formula = 2 * (C3H6O)

= C6H12O2