On analysing an impure sample of sodium chloride, the percentage of chlorine was found to be 45.5. What is the percentage of pure sodium chloride in the sample ?

Explanation

Molar mass of pure NaCl = `23+35.5=58.5"g mol"^(-1)`
`% " of Cl in pure NaCl "=(35.5)/(58.5)xx100=60.6`
Thus, 60.6 parts of Cl are present in 100 parts of pure NACl
45.5 parts of Cl will be present in pure NaCl `=(100)/(60.6)xx45.5="75 parts"`
The remaining `25%` is impurity present in impure sample.
Hence, `%` of pure NaCl in impure sample = `75%`.