# Molality Calculator

Note
• Enter the values of the three known values
• Click on the calculate button.

Formula used
$Molality=\frac {mass}{MolarMass \times Weight \; of \; Solvent}$

## What is Molality

Molality is one of the unit of measuring concentration of Solution. It is defined as the Number of moles of solute per kg of solvent. It is denoted by letter m
Molality formula is given by
$\text{Molality}=\frac {\text{mass}}{\text{Molar Mass} \times \text{Weight of Solvent}}$
Where
mass -> Mass of the solute
Molar Mass -> Molar mass of the Solute
Weight of Solvent -> Weight of Solvent(kg)
Unit of Molality is mol/kg

Example of Few questions where you can use this formula
Question 1
What's the mass of NaCl required to make a 0.2 m of NaCl solution in 800gm of water? The molar mass of NaCl is 58.44276 g/mol.
Solution
Given , Molar Mass=58.44276 g/mol, Molality = .2 m, Weight of Solvent = 800 gm = .8 kg, Mass=?
Molality formula is given by
$\text{Molality}=\frac {\text{mass}}{\text{Molar Mass} \times \text{Weight of Solvent}}$
Rearranging for Mass
$\text{mass}= \text{Molality} \times \text{Molar Mass} \times \text{Weight of Solvent}= .2 \times 58.44276 \times .8=9.35 gm$
Question 2
What is the mass of the solvent of a 0.1 m HCl solution containing 1.46 grams of HCl?. The molar mass of HCl is 36.5 g/mol.

Solution
Given , Molar Mass=36.5 g/mol, Molality = .1 m, Weight of Solvent = ?, Mass=1.46 gm
Molality formula is given by
$\text{Molality}=\frac {\text{mass}}{\text{Molar Mass} \times \text{Weight of Solvent}}$
Rearranging for Weight of Solvent
$\text{Weight of Solvent}=\frac {\text{mass}}{\text{Molar Mass} \times \text{Molality}}= \frac {1.46}{36.5 \times .1}=.39 kg$

## How this Calculator works

• if mass, Molar Mass and weight of solvent is given ,then Molality calculation done as below formula
$\text{Molality}=\frac {\text{mass}}{\text{Molar Mass} \times \text{Weight of Solvent}}$
• if mass, Molality and Weight of solvent is given ,then Molar Mass calculation is done as below formula
$\text{Molar Mass}=\frac {\text{mass}}{\text{Weight of solvent} \times \text{Molality}}$
• if Mass, Molality and Molar Mass is given ,then Weight of solvent calculation is done as below formula
$\text{Weight of solvent}=\frac {\text{mass}}{\text{Molar Mass} \times \text{Molality}}$
• if Weight of solvent, Molality and Molar Mass is given ,then mass calculation is done as below formula
$\text{mass}= \text{Molality} \times \text{Molar Mass} \times \text{Weight of solvent}$

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