Question

The 5.85 g of NaCl and one kg of water is added
to prepare a solution. What is the strength of
NaCl in this solution ?
(Molecular weight of NaCl = 58.5)
(a) 0.1 Normal (b) 0.1 Molal
(c) 0.1 Molar (d) 0.1 Formal

Answer 1

Given - weight of NaCl - 5.85 g

Molecular weight of NaCl - 58.5 g

Weight of solvent - 1kg

Find - Strength of solution

Molality is a property of solution. It is defined as the number of moles of solute per kilogram of solvent. It is mathematically represented as -

M = n/w(kg)

Where M is molality, n is number of moles of solute and w is weight of solvent in kilogram.

Number of moles is ratio of weight of solute to the molecular weight.

Keeping values in formula -

M = (5.85/58.5)/1

M = 0.1 molal

Hence, strength of NaCl is

b) 0.1 molal.