Empirical Formula

Question 1

What is the empirical formula?

Answer 1

The empirical formula of a substance

is the simplest whole-number ratio of atoms in a compound.

Question 2

How do we calculate the empirical formula?

Answer 2

1. Find the number of moles of each element.
   
   • Divide the mass or percentage of the element by its relative atomic mass.
2. Divide each calculated amount by the smallest number of moles.
3. Write out the formula.

Question 3

Compound X is made up of 72g of carbon and 12g of hydrogen. Explain how to find its empirical formula.

Answer 3

1. First find the number of moles of each element.
   
   • C: 72/12 = 6 moles
   • H: 12/1 = 12 moles
2. Divide each amount by the smallest number of moles.
   
   • C: 6/6 = 1
   • H: 12/6 = 2
3. Empirical formula: CH2