Question

Determine the empirical formula of the following compound if a sample contains 0.104 molK, 0.052 molC, and 0.156 molO.

Answer 1

The empirical formula is K₂CO₃.  

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

The ratio of atoms is the same as the ratio of moles, so our job is to calculate the molar ratio of K:C:O.  

I like to summarize the calculations in a table.  

Element Moles  Ratio¹ Integers²  

     K       0.104   2.00         2

     C       0.052  1.00          1

     O      0.156   3.00         3

¹ To get the molar ratio, you divide each number of moles by the smallest number.  

² Round off the number in the ratio to integers to integers (2, 1, and 3).

The empirical formula is K₂CO₃.