Question

A certain compound contains 4.0 g of calcium and 7.1 g of chlorine. Its relative molecular mass is 111. Find its empirical and molecular formulas

Answer 1

Given :

A certain compound contains 4.0 g of calcium and 7.1 g of chlorine.

Its relative molecular mass is 111.

To Find :

Its empirical and molecular formulas.

Solution :

Moles of calcium , $n_1=\dfrac{4}{40}=0.1\ moles$.

Moles of chlorine , $n_2=\dfrac{7.1}{35.45}=0.2\ moles$ .

The ratio calcium and chlorine is 1 : 2 .

So , the empirical formula is $CaCl_2$ .

Now , molecular mass of $CaCl_2$ is :

$M=40+(2\times 35.45)\\\\M=110.9\ g$

So , $n=\dfrac{111}{110.9} \approx1$

Therefore , the molecular formula is also $CaCl_2$ .

Hence , this is the required solution .