When looking at a titration curve, I have to determine which is not true and I have it narrowed down to two options:
The initial starting point on the titration curve is where pH depends only on [HA]0
or
The finial point on a titration curve the pH depends only on [A-]
I would think the first option would be first? Considering the finial point would be where only the excess base is left over, but I'm not sure.
To determine which statement is not true regarding a titration curve, let's first understand the basics of a titration. A titration involves the reaction of an acid (HA) with a base (OH-) in a controlled manner. The goal is to determine the concentration of either the acid or the base by adding a solution of known concentration until the reaction reaches its equivalence point.
During a titration, pH is measured and plotted against the volume of the added solution. A titration curve is obtained, which typically shows a gradual change in pH followed by a sharp transition at the equivalence point.
Now, let's analyze the two statements:
1. "The initial starting point on the titration curve is where pH depends only on [HA]0."
2. "The final point on a titration curve, the pH depends only on [A-]."
Based on the nature of the titration, let's evaluate each statement:
1. The initial point of a titration curve is when no base has been added yet, meaning it is still in the acid form (HA). At this point, the pH depends on the concentration of the acid, [HA], as it has not reacted with any base yet. Therefore, the statement is generally true.
2. The final point of a titration curve is the equivalence point, where the acid and the base have reacted in stoichiometric proportions. At this point, all the acid has been neutralized, and only the conjugate base (A-) remains. Considering this, the pH should depend only on the concentration of [A-], not the acid [HA]. Thus, the statement is also generally true.
Given these evaluations, it appears that both statements are generally true, and you will need to reevaluate your narrowed-down options. It's also possible that the discrepancy lies in some other aspect of the statements or an additional option that has been overlooked.