Imagine that you are attempting to determine the concentration of an acid by tit
ID: 977902 • Letter: I
Question
Imagine that you are attempting to determine the concentration of an acid by titration with a solution of sodium hydroxide with a known concentration, using phenolphthalein as an indicator. For each of the following sources of error, indicate whether the calculated concentration of acid would be too high or too low. An air bubble was present in the tip of the buret before beginning the titration but was absent at the end of the titration. You added too much base and went beyond the end point. Some of the acid splashed on to the sides of the flask and wasn't titrated. What is the purpose for performing part A (Standardization of Sodium Hydroxide) in this experiment?Explanation / Answer
1. i) Presence of an air bubble in the burette would result in over reading of the titrant volume and therefore the calculated value of the acid concentration will be more than the actual value.
ii) Addition of greater amount of base even after the end point, would result in higher calculated value of the acid's concentration as the volume of base used for the titration with the acid is read as more than actually required.
iii) When some of the acid is splashed over the walls of the flask, the volume of NaOH used to react with the acid in the flask is under read. This leads to lower calculated values of the acid's concentration.
2. NaOH is the secondary standard and is therefore standardized before the titration with an acid so as to get an idea of it's exact concentration.