Question

How can I convert between molarity and molality?

Answer 1

Hint: [The molar concentration of a solution. Which is expressed as the number of moles of solute per liter of solution. Whereas malolity also the measurement of molar concentration it is the moles of solute per kilogram of a solvent.]

Complete step by step answer:
Formula for molarity:
Concentration $(M)=\dfrac{n}{v}=\dfrac{\text{number of moles}}{\text{volume}}$
Where,
$M=$ molar concentration
$n=$ moles of solute
$v=$ litres of solution.
Unit $=$ moles liter
Formula for molality
Molality $(m)=\dfrac{\text{Number of moles of solute}}{\text{mass of solvent in kilogram}}$
Relation between molarity and morality
$\dfrac{1}{m}=\dfrac{d}{m}=\dfrac{Ms}{1000}$
Where
$m=$ molarity of solution
$M=$ molarity of solution
$d=$ density of solution in g/m
${{M}_{s}}=$ Molar mass of solute
Above we have both the formula for molarity $(M)$ and molarity $(m)$ so we can easily convert by knowing one quantity ester molarity or molality is both the number of moles of solute remains same but in molarity we talking about volume in liter whereas in molality we should have mass of solvent in kilograms. And we also have the relation between molality and molarity in the above formula then by knowing the density of solution in grams per milliliter and molar mass of solute we have the molality or molarity.

Note: Both are the concentration of the solute respect to volume sometimes we have volume in liter and sometimes we have in gram or kilograms when we are talking about the solids then we have molality and when we are talking in liquid manner then we have molarity.
By calculating molarity and modality we can calculate other terms also. These both terms are very important and help to calculate many important quantities in ‘solution part of chemistry.’ When we study about the properties of any solution first we have knowledge about the molarity normality and molality of that solution.