Question

What, if any, effect would result from calculating saturation concentration when there was a lot excess solid urea suspended in solution after saturation was reached?

a. Saturation concentration would be falsely low

b. There would be no effect

c. Saturation concentration would be falsely high

Answer 1

Saturation is a state of solution when it is incapable of dissolving any more solute. If we add more solute to it, two cases arise:
Either the added (excess) solute will come out as precipitate or it won't dissolve at all.
So after achieving saturation, a saturation concentration is attained and if we add more of the solute to it, there would be no change in this saturation concentration.
In the case given above, the solute is solid urea and the solution has achieved saturation, therefore on adding more solid urea, it would be considered exess urea and won't dissolve in it, and remain suspended. Hence it won't make any change to the saturation concentration.
Hence the option b) would be most preferable one and is correct under given conditions as there won't be any effect of excess urea on the calculation of saturation concentration.
Option a) and option c) are not possible as per above explanation.
One might think that option c) is correct as the excess suspended urea would add to the saturation concentration, but in that case if any excess urea adds to the saturation concentration, a similar amount of dissolved urea would precipitate out and therefore making the saturation concentration same as before i.e overall no effect on saturation concentration.

Therefore we again reach on option b) as the correct option.