Question

How can I calculate the empirical formula of copper sulfide?

Answer 1

Hint: Empirical formula can be defined as the simplest mathematical formula which provides us information about the lowest whole number ratio of atoms existing in a given compound. Relative number of atoms of every element in the compound is provided with the help of this formula.

Complete step by step answer:
In this case we have to calculate the formula for copper sulfide which can be calculated by the following method or by performing following lab experiment:
First we have to heat a mixture of copper and sulfur in order to produce a sample of copper sulfide.
After that weigh the empty crucible and find a weight which suppose x g
Then weight the crucible with the copper and find a weight which comes y g
And then crucible + copper sulfide and find a weight of which comes to be z g.
Now find the percent composition of the copper sulfide and its empirical formula.
We know that the mass of copper is equal to
$m_{copper}$= (Weight of crucible + copper) – weight of crucible
$m_{copper}=y-x=A$
Similarly mass of copper sulfide is given by = (Weight of crucible + copper sulfide) – weight of crucible;
$m_{coppersulfide}=z-x=B$g
Which represents that the mass of sulfur is
$m_{sulfur}=m_{copper\text{sulfide}}\text{ - }{\text{m}}_{\text{copper}}$= A – B = C
The percentages of copper and sulfur in the copper sulfide are given as
$$ = M
$$ = N
This represents that, for every 100 g of copper sulfide, you get Mg of copper and Ng of sulfur.
You now divide each element's percentage by its molar mass to get the mole ratio of the two elements in the formula
When we put the values of every observation then we find the mole ratio to be 1:1.
Thus we can say that empirical formula is $C{u}_1{S}_1$ i.e. $$CuS$$.

Note: To determine the empirical formula for any compound we have to know about the mass of one reactant and the mass of the product or about the percent composition of the compound. Reactant is that species which are starting one i.e. who reacts with each other to form the final product which is known as product.