Question

What is molality????​

Answer 1

Answer:

Molality is a property of a solution and is defined as the number of moles of solute per kilogram of solvent.

The SI unit for molality is mol/kg.

A solution with a molality of 3 mol/kg is often described as “3 molal” or “3 m.”

However, following the SI system of units, mol/kg or a related SI unit is now preferred.

Lets understand it with an example :-

If 300 g of sugar, C12H22O11, are dissolved in 1500 g of water, what is the molality of the solution ?

Molality = number of moles/weight of solvent (kg)

Number of moles of sugar = conc. (g)/molar mass

Molar mass of C12H22O11 = 12x12 + 1x22 + 16x11

= 144 + 22 + 176 = 342 g/mol

Number of moles of sugar = 300/342 = 0.877 mols

Therefore,

Molality = 0.877 mols/ 1.5 kg = 0.585 m ...

Answer 2

Molality :

• Molality is a measure of number of moles of solute present in 1 kg of solvent.

• This contrasts with the definition of molarity which is based on a specified volume of solution. A commonly used unit for molality in chemistry is mol/kg.

• A solution of concentration 1 mol/kg is also sometimes denoted as 1 molal.

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