Question

Commercial bleaching solution contains $3.62$ mass percentage of sodium hypochlorite $\left(NaOCl\right)$ in water. Calculate the molality of the solution

• A. $1.08m$
• B. $0.504m$
• C. $0.252m$
• D. $0.854m$

Answer 1

The correct option is B $0.504m$

Given

Mass % of NaOCl is 3.62

Solvent is Water

Solution

Mass percentage means mass of solute in 100 g of solution

This means 3.62g of NaOCl is dissolved in 100g of solution

Molality is Moles of solute per kg of solvent

Here solvent is water

Moles will be mass of solute/molecular mass of solute

Molecular mass of NaOCl is 23+16+35.5=74.5g

moles= 3.62/75.5=0.04859

Mass of solvent will be mass of solution -mass of solute

Mass of water=100g-3.62g=96.38g=0.09638

Molality =0.04859/0.09638

=0.504

The correct option is B