Question
Mention two units for expressing the concentration of a solution. How can you convert from one unit to the other?
Answer
Two units for expressing the concentration of a solution are molarity (M) and molality (m).
Molarity (M) = moles\ of\ solute\over volume\ of\ solution\ (in\ litres)
Molality (m) = moles\ of\ solute \over mass\ of\ solvent\ (in\ kilograms)
To convert from molarity to molality or vice versa, we need to know the density of the solvent. We can use the following formula:
Molarity = molality × molecular\ weight\ of\ solute \over\ density\ of\ solvent × 1000
Molality = Molarity × density\ of\ solvent × 1000 \over molecular\ weight\ of\ solute
By using the density and molecular weight values, we can convert between molarity and molality.
