Help me please to answer on this question: 1. Suggest reasons why your experimen
ID: 1043584 • Letter: H
Question
Help me please to answer on this question:
1. Suggest reasons why your experimental values (Ksp.average = 5.48*10^-5 at 23oC) might be higher or lower that the literature values (Ksp = 5.5*10^-6 at 25oC). Possibilities may include:
a) You added several mL of acid at a time, rather than adding acid drop-by-drop as you approached the equilibrium point.
b) A trace of acid impurity may have been present in the Erlenmeyer flask at the beginning of the titration.
c) It may have been more difficult detecting the endpoint when titrating a base with an acid (vs. a base with an acid), because….
Explanation / Answer
When the solution contained some solids, it was known that it is saturated. Since this solution was saturated it was implied that it was at equilibrium. Being at equilibrium the forward reaction had to equal the reverse reaction. This implied that the dissolving and crystallization reactions happened at an equal rate and simultaneously. For these reactions to be equal, some precipitate would have been present, indicating the saturated solution was at equilibrium.It was necessary to remove all of the solid base before titrating because the it would have affected the rate of reaction. When the acid was titrated with base, some of the solid would go down with the liquid because of a minuscule amount of filtering.. Since the solids were really concentrated, it would have many reactions with the acid. Therefore, the amount of base had to be only liquid, with no solid pieces going into the burette, which would have neutralized the acid too quickly.
Filtering the base can’t be done perfectly with the equipment used in this lab. Without a pure solution (of base) the amount of the solution would change that was needed to titrate the acid . The value of solution went up thus giving a different value then was first assumed for Ksp. The less that was filtered lead to a higher value for the Ksp then first thought.
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