Question

Addition of hgi2 to ki (aq.) shows decrease in vapour pressure. why

Answer 1

HgI2 forms a complex with KI and therefore number of particles in the solution decreases. HgI2 + 2KI => K2[HgI4] Vapor pressure is a property that binds molecules together, decrease in the number of solute particles will increase the vapor pressure and therefore it will show increase in vapor pressure no decrease will be noted.

Answer 2

Freezing point of the solution will increase. Mercuric Iodide will react with Potassium Iodide to form dipotassium tetraiodomercury. The reaction is given below : 2KI + HgI2 = K2[HgI4] This association will decrease the number of ions in the solution as a result of which Van't Hoff Factor (i) will decrease as ndecreases from 4 to 3.