Answer to Question #146490 in General Chemistry for Gusty

Question

3. Describe the effect of the following factors (whether the increase, decrease, or has no effect)
on the actual yield of CaCO3 (s).
a. Using a coarse filter paper instead of one with fine porosity.
b. Insufficient washing of the precipitate.
c. If the precipitate is washed with an acidic solution.
d. If the precipitate was not dried completely.

Answer 1

a. If coarse filter paper had been used instead of one with fine porosity, the reported percent of

limiting reactant been low, because if some of the fine precipitate had gone through the paper

instead of being retained and weighed, the mass of precipitate would be low, and the precipitate

mass is used to calculate the mass of the limiting reactant, and thus the percent of limiting

reactant.

b) The purpose for washing the precipitate i is to remove all of the

ions from

the solution around the precipitate. If the ions were to be left in the solution around the

precipitate when the precipitate dried, evaporation would leave the ions behind, raising the

weight of the precipitate, and increasing the calculated amount of limiting reactant.

c) If the precipitate is added to an acid, it reacts with it to form a trioxocarbonate, salt and water. So the concentration reduces as the reaction is going on

d) we will have the mass of the precipitate and some of the solution so the actual yield will increase