Question

What is the molality of a solution of 10 g NaOH in 500 g water?

Answer 1

The molality is 0.50 mol/kg.

molality = `("moles of [solute](http://socratic.org/chemistry/solutions-and-their-behavior/solute)")/("kilograms of [solvent](http://socratic.org/chemistry/solutions-and-their-behavior/solvent)")`

moles of NaOH = 10 g NaOH × `(1"mol NaOH")/(40.00"g NaOH")` = 0.25 mol NaOH

kilograms of H₂O = 500 g H₂O × `(1"kg H₂O")/(1000"g H₂O")` = 0.500 kg H₂O

molality = `("moles of solute")/("kilograms of solvent") = (0.25"mol")/(0.500"kg")` = 0.50 mol/kg