In: Chemistry
Question: Explain whether the technique errors will result in high or low experimental determination of the molar concentration of CH3COOH in vinegar. 1. A student uses the pipet bulb to blow the last bit of vinegar sample from the tip into the titration flask, after the pipet is drained. 2. A student fails to clean the pipet first, After delivering the vinegar sample, the student notices a drop of vinegar clinging to the inner surface of the pipet. 3. A student stops the titration when the pink persists throughout the solution for less than 10 seconds after completing the titration, a student notices that buret is not clean. Droplets of NaOH solution are clinging to the inner surface of the buret. Briefly explain why adding distilled water to the vinegar sample prior to the beginning titration does not affect the results of your determination of the molarity of CH3COOH in your vinegar sample.
Technique errors and experimental determination of molar concentration of vinegar
1. If the student blows the last bit of vinegar sample in the titration flask, the molar concentration of vinegar would be higher than the actual value. The last bits of vinegar added would take additional base for neutralization which would give a false value.
2. In case the student failed to wash the pipet, the molar concentration of vinegar would be low. Failure to wash the pipet would result in mixing of the water present in pipet with the vinegar which would dilute the vinegar solution and thus low volume of base would be used for neutralization which would account of low molar concentration.
3. If the student stops the titration too soon, that is the color persists only for few seconds with NaOH clinging on the inside of buret wall, false end point or neutralization point would be recorded when the actual vinegar is not neutralizaed in solution at the time. This thus uses low amount of base and would give a low molar concentration value for vinegar by titration.
4. Adding distilled water does not effect the overall concentration of vinegar in solution used for molar concentration determination via titration with a base. The total amount of vinegar remains the same even after adding distilled water and thus the molar concentration remins exactly the same.