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

$(a)\;80\qquad(b)\;65\qquad(c)\;75\qquad(d)\;95$

The molecular mass of pure sodium chloride (Nacl)=At mass of Na+At mass of chloride
$\Rightarrow (23+35.5)$
$\Rightarrow 58.5$
% of chlorine in pure Nacl=$\large\frac{35.5}{58.4}$$\times 100=60.6 Thus % of purity of Nacl in the sample=\large\frac{45.5}{60.6}$$\times 100$
$\Rightarrow 75$
Hence (c) is the correct answer.