Question

The percentage of available chlorine in a pure bleaching powder (${\mathrm{CaOCl}}_2$) sample is ______.

Answer 1

The percent by weight:

• It is also referred to as mass percent composition and is expressed as W/W% meaning weight by weight.
• It is defined as the ratio of the mass of a solute and the mass of the solution multiplied by $100$.

Step 1: Given data

• The total molecular weight of bleaching powder ${\mathrm{CaOCl}}_2$ is $127$ g/mol with calcium, oxygen, and chlorine contributing$40$, $16$ and $71$ g/mol respectively.

Step 2: Use the formula

• Use percent by weight formula i.e. W/W%
• Here mass of solute is the total mass of all the chlorine atoms present in bleaching powder and the mass of solvent equals the mass of bleaching powder.
• Mass due to chlorine = $71$ g/mol.
• Therefore, percentage chlorine by weight = $\frac{71}{127}\times 100$= $55.9\%$

Thus, the percentage of available chlorine in a pure bleaching powder (${\mathrm{CaOCl}}_2$) sample is $\mathbf{55}\mathbf{.}\mathbf{9}\mathbf{\%}$.