Question

Calculate the empirical formula of a compound containing 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass.

• A. $ \text{CH}_2\text{O} $
• B. $ \text{C}_2\text{H}_4\text{O} $
• C. $ \text{CHO}_2 $
• D. $ \text{C}_2\text{H}_6\text{O} $

Hint:

To find empirical formula, divide each element's moles by the smallest and simplify to whole numbers.

Answer 1

The Correct Option is A

Assume 100 g of compound:

C = 40 g → $ \frac{40}{12} = 3.33 \, \text{mol} $

H = 6.7 g → $ \frac{6.7}{1} = 6.7 \, \text{mol} $

O = 53.3 g → $ \frac{53.3}{16} = 3.33 \, \text{mol} $
Divide by smallest mole value (3.33):

C: 1, H: 2, O: 1
Empirical formula:
$$ \text{CH}_2\text{O} $$