Question

Which statement is incorrect?
-In a saturated solution the rate of dissociation is equal to the rate of precipitation;
-In a saturated solution, the amount of dissolved solute depends on the amount of undissolved solute on the bottom of the flask.

Answer 1

Hint: Remember whatever you learnt about the saturated, unsaturated and supersaturated solutions. For statement one, you have set up an equilibrium between dissolved and undissolved salt. Read the second statement carefully: the amount of dissolved solute does not depend on the amount of undissolved solute.

Complete Step By Step Answer:
For the first statement, if a solution contains less than the maximum solute, it is unsaturated. When a solution is saturated and excess solute is present, the rate of dissolution is exactly equal to the rate of crystallization or precipitation. A saturated solution that was prepared at a higher temperature usually contains more dissolved solute than it would contain at a lower temperature. A supersaturated solution is usually unstable, consequently, adding a small particle of the solute will usually cause the excess solute to rapidly precipitate or crystallize, sometimes with spectacular results. In contrast, adding a seed crystal to a saturated solution reestablishes the dynamic equilibrium, and the net quantity of dissolved solute no longer changes.
For the statement- A solution with a solute that dissolves until it is unable to dissolve any more, leaving the undissolved substances at the bottom.
Therefore, by the above information, we can say that the second statement is incorrect.

Note:
If a saturated solution is cooled below the temperature at which the solution is prepared, then it will lead to a decrease in the solubility of the solute. Again, if this solution is heated, the crystals would dissolve in the solution and no longer be visible.