Question

Determine the empirical formula of the compound if is analyzed and found to be composed of $75$% carbon and $25$% hydrogen?

• A. $C_2{H}_4$
• B. $C{H}_4$
• C. $C{H}_3$
• D. $C{H}_2$
• E. $CH$

Answer 1

The correct option is B $C{H}_4$

The compound is found to be composed of 75% carbon and 25% hydrogen.
100 g of the compound contains 75 g of carbon and 25 g of hydrogen.
The atomic masses of carbon and hydrogen are 12 g/mol and 1 g/mol respectively.
The number of moles of C $=\frac{\text{75 g}}{\text{12 g/mol}}=\text{6.25 moles}$
The number of moles of H $=\frac{\text{25 g}}{\text{1 g/mol}}=\text{25 moles}$
The mole ratio $C:H=6.25:25=1:4$
The empirical formula of the compound is $C{H}_4$.