Answer to Question #147511 in General Chemistry for Gusty

Question

1. State the effect of each of the following factors on the calculated molarity of
NaOH and the reported value of the unknown strong acid.
a. A drop of NaOH adheres to the side of the conical flask during the
standardization of NaOH solution.
b. Adding 10 drops of phenolphthalein indicator rather than 2 drops in the
standardization of NaOH.
c. An air bubble is originally trapped in the buret tip but disappears during titration.
d. Addition of distilled water to the conical flask during titration.

Answer 1

a. A drop of NaOH adheres to the side of the conical flask during the

standardization of NaOH solution : the calculated molarity of NaOH will be lower than the true one, as not all NaOH reacts during the standardization.

b. Adding 10 drops of phenolphthalein indicator rather than 2 drops in the

standardization of NaOH: the calculated molarity of NaOH will be higher than the true one, as a part of acid added will have to be used to neutralize the excess of indicator in the solution.

c. An air bubble is originally trapped in the buret tip but disappears during titration: the true amount of the NaOH added will be smaller than the one noted, so the reported concentration of the unknown acid will be higher than the true one.

d. Addition of distilled water to the conical flask during titration: the addition of the distilled water to the conical flask during the titration will have no effect.