Question

What is the difference between molality and molarity? Why do these values tend to be very similar in aqueous solutions?

Answer 1

Molality is the number of moles of solute per kilogram of solvent, where as molarity is number of moles of solute per Litre of soluion (notice that its solution this time)

For aqueous solutions (solutions where water is the solvent) near room temperature, the difference between molar and molal solutions is nearly nill. This is because around room temperature, water has a density of 1 kg/L. This means the "per L" of molarity is equal to the "per kg" of molality.