Question

molality deft with illastration please give information this topic.

Answer 1

m = moles/kg solvent

28.4g Na2SO4 in 500 g H2O.
moles = 28.4/molar mass Na2SO4 = 28.4/142 = 0.2
0.2/kg solvent = 0.2 moles/0.5 kg = 0.4 m.