Question

Calculate the molality of a solution containing `20g` of sodium hydroxide `(NaOH)` in `250g` of water ? .

Answer 1

Moles of sodium hydroxide `=20 //40 = 0.2` mol `NaOH`
`250 gm = 0.25kg` of water
Hence molality of solution =Mole of solute/Mass of solvent `(kg) = 0.2 mol//0.25kg`
or Molality `(m) = 0.8 mol//kg` or `0.8m` .