# The density of the 3M solution of NaCl is 1.25 gram per ml . Calculate molality of the Solution.

By Shivank Goel|Updated : August 11th, 2022

Given, that the density of 3M solution of NaCl is 1.25 g/ml

We have to find the molality of the solution.

Molality is defined as the number of moles of solute present per kg of solvent. Its unit is mol/kg. It is denoted by m.

Molality = [moles of solute(mol)/weight of solvent(kg)] x 1000

Molarity also known as the molar concentration of a solution is defined as the moles of a solute per liters of a solution. It is denoted by M.

Molality can be related to molarity using the density of the solution as

m = Mx1000/ (1000ρ - Mxw)

Where M = Molarity

m = molality

ρ = density of the solution in g/ml

w = molecular weight (molar mass) of solute in g/mole

Here, w = 58.44 g/ml

So, m = 3x1000 / (1000x1.25 - 3x58.44)

= 3000 / (1250 - 175.32)

= 3000 / 1074.68

= 2.79 mol/kg

Therefore, the required molality is 2.79 mol/kg.

Summary:

## The density of the 3M solution of NaCl is 1.25 grams per ml. Calculate the molality of the Solution.

The density of the 3M solution of NaCl is 1.25 grams per ml. The molality of the solution is 2.79 m.

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