Empirical formula

Empirical formula is the simplest (smallest) ratio of the each type of atom in a formula.

eg: In a compound having a formula of C6H12O6  find the empirical formula

elements                                    C :  H :  O

Original ratio in the compound     6 : 12 : 6

Simplest ratio                              1 : 2  :1

Empirical formula = CH2O

It is possible to calculate the empirical formula by obtaining the percentage by mass of a compound

e.g. A sample of the compound was analysed and found to contain 0.72 g of

carbon, 0.18 g of hydrogen and 0.96 g of oxygen. Find the empirical formula of the compound

1. Write the elements present in the compound 

       C                     H                    O

2. Write the percentages of masses in each element

      0.72                 0.18                 0.96

3. Find the mole ratio of each atom by dividing the percentage mass by the relative atomic mass

      0.72/12            0.18/1              0.96/16

       =0.06              =0.18                = 0.06

4. Divide by the smallest number to get a whole number ratio (if this step does not produce whole numbers try more divisions, multiplications and rounding up)

     0.06/0.06          0.18/0.06             0.06/0.06

     =1                     =3                     =1

5. Now you can write the empirical formula by using the above ratios

 CH3O

Arunigd 11:57 PM   calculating empirical formula   empirical formula   example empirical formula   finding empirical formula   GCSE Chemistry

Author : Arunigd

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