Question

How many chlorine atoms are there in seven sodium chloride formula units?

Answer 1

The number of formula units of NaCl are 7. In 1 mole of NaCl there are
`6.023* 10^(23)` formula unit are present.

Thus, 1 formula unit will be there in
`(1)/(6.023* 10^(23))=1.66* 10^(-24)` moles.

and, 7 formula unit will be there in
`1.16* 10^(-23)` moles.

There is 1 mol of Cl present in 1 mol of NaCl. thus,
`1.16* 10^(-23)` of Cl will be there in
`1.16* 10^(-23)` mol of NaCl.

Converting number of moles into number of atoms as follows:

In 1 mole of a substance there are
`6.023* 10^(23)` atoms of chlorine thus, in
`1.16* 10^(-23)` mol there will be 7 atoms of chlorine.

Therefore, number of atoms of chlorine will be 7.