Chemistry for Environmental Engineering and Science (5th Edition)
Transcribed text From Image:
Expert Chegg Question Answer:
Would the analytical results by the Mohr method for chloride be higher, lower, or the same as the true value if an excess of indicator were accidentally added to the sample? Why?
- Step 1 of 2 The Mohr method makes use of silver nitrate solution for titration. This solution can be standardized against standard chloride solutions prepared from pure sodium chloride. During titration, the chloride ion is precipitated as white silver chloride. The reaction occurs as follows:
- Step 2 of 2 The most commonly used indicator in the Mohr method is potassium chromate, as it provides chromate ions. As the titration proceeds, the concentration of chloride ion decreases, while that of silver ion increases. The silver ions combine with the chromate ions to form a reddish-brown precipitate of silver chromate when the concentration of silver ion exceeds the solubility product of. The formation of the colored complex indicates the endpoint of the titration and suggests that all chloride ions present in the sample are consumed. The reaction occurs as follows: If an excess amount of indicator is used, the concentration of silver ion in the sample will exceed the solubility product of, and the end point will be observed much earlier than the actual one. Therefore, the analytical results for chloride will be lowered in the presence of an excess amount of indicator