This is the chemical formula for acetic acid (the chemical that gives the sharp taste to vinegar): an analytical chemist has determined by measurements that there are 3.2 moles of carbon in a sample of acetic acid. How many moles of oxygen are in the sample?

Acetic Acid having chemical formula C₂H₄O₂ and structural formula attached below is the second member of carboxylic family in organic compounds. It is commonly used as vinegar i.e. a mixture containing 5 % Acetic acid and 95 % water.

As shown in structure 1 mole of Acetic acid contains 2 moles of Carbon atoms, 4 moles of Hydrogen atoms and 2 moles of Oxygen atoms respectively. Hence, the number of moles of Oxygen atoms contained by acetic acid containing 3.2 moles of Carbon is calculated as,

2 moles of C accompany = 2 moles of O

So,

3.2 moles of C will accompany = X moles of O

Solving for X,

X = (3.2 mol C × 2 mol O) ÷ 2 mol C

X = 3.2 mol of Oxygen