Question

rate of crystallization from saturated solution may be increased hy(seeding/heating)​

Answer 1

Answer:

Saturation describes an equilibrium condition, viz.:

Solid solute

⇌

Dissolved solute

And thus, in a saturated solution, we might typically see some UNDISSOLVED solute, i.e. a crystalline residue, on the bottom or the sides of the flask.

For a given solvent (usually water), a temperature is specified because a hot solution can normally dissolve more solute than a cold solution.

And now attend, because this definition seems to cause a lot of confusion. If the solution contains a GREATER amount of SOLUTE than would be in equilibrium with UNDISSOLVED solute (i.e. a greater amount of solute than does the saturated solution), the solution is said to be

supersaturated

.

How could we make a

supersaturated solution

? Well, one way might be to take a saturated solution (with a mass of undissolved solute), give it a good heat blast to bring ALL of the SOLUTE into solution, and cool the flask carefully, so that the crystals do not precipitate out of solution.

Supersaturation

is a metastable condition, and sometimes, the solution can be brought back to equilibrium, to

saturation

, by scratching the sides of the flask, or introducing a seed crystal, and a mass of solute precipitates; sometimes it does so and generates a lot of heat, which represents the heat required initially to bring the solute to supersaturation. After the mass of crystals deposit, the solution is

NOW SATURATED.

Answer 2

Answer:

rate of crystallation from saturated solution may be increased by