Question

Calculate the molality of solution containing 5.3 gm of sodium carbonate in 400 gm of water.

Answer 1

Given, weight of Na₂CO₃ =5.3g

           weight of water = 400g = 0.4kg

Gram molecular weight of Na₂CO₃ is 106g

=> Number of moles of Na₂CO₃= 5.3/106

                                                          =1/20        

   molality = number of moles of solute/ mass of solvent(in kg)

 =>molality=(1/20)/(0.4)=0.125