Question

How do you calculate the empirical formula of a compound?

Answer 1

Hint: We need to know and study the concept of empirical formula and how can it be calculated. Empirical formula shows the simplest whole-number ratio of atoms. Calculating the percentage composition of the constituent elements of a compound is the key to calculate the empirical formula. A set of rules are to be followed which will be studied.

Complete step by step answer:
We need to remember that the empirical formula is calculated using the following rules:
The mass of each of the constituent elements is converted to moles using the respective atomic weights.
Each mole value is divided by the smallest number of moles calculated.
The mole ratio of the elements is represented as the subscripts as the empirical formula.
Let us consider an arbitrary compound ${A_x}{B_y}$ . The empirical formula can be calculated by finding the values of x and y. Firstly the percentage composition of each of the constituent elements of the compound is calculated. This is followed by the number of moles of $x$ and $y$ calculated in the compound. Then each mole value is divided by the smallest number of moles calculated. If they are in decimal numbers, they are converted into whole numbers which replaces the values of $x$ and $y$ in the compound ${A_x}{B_y}$ . This gives the empirical formula of the compound.

Note: It must be noted that the percentage composition calculation of each of the constituent elements of a compound is the most necessary step to calculate the empirical formula of a compound. Empirical formula and molecular formula need not be the same. Empirical formula shows the simplest whole-number ratio of atoms in a compound whereas molecular formula shows the number of each type of atom in a molecule.