Question

(a) A solution contains 30g of common salt in 330g of water. Calculate the concentration in terms of mass by mass percentage of the solution. (b) Give two reasons to explain that crystallization is batter technique than evaporation for obtaining pure substance from its impure sample. Mention its two applications. (c) How will you convert a saturated solution into an unsaturated solution without adding a solvent?


plz answer and help me

Answer 1

b.Crystallisation is a process that separates a pure solid in the form of its crystals from a solution.
Crystallisation is better than evaporation because during Evaporation
• Some solids decompose or some, like sugar may get charred on heating to dryness.
• Some impurities may remain dissolved in the solution even after filtration which on evaporation contaminates the solid.

c.If the solubility of the solute in the solvent is directly proportional to the temperature, then increasing the temperature of the system will make a saturated solution unsaturated. There may be other ways too, but I think the easiest way would be to just add more solvent. The simplest way is to add more solvent.

a. Mass of common salt = 30g
Mass of water = 320 g
Percentage of solution = (Mass of substance/Mass of water)*100
= 30/320 * 100

=9.375