Students performing vinegar analyses made several mistakes in their experiments.
ID: 807064 • Letter: S
Question
Students performing vinegar analyses made several mistakes in their experiments. Explain in detail how each error below will affect the final result (% weight of acetic acid in vinegar) of each student's experiment. Show all steps of logic followed in analyzing the effects of the mistake (remember that the experiment had two parts):1.Student A used a wet beaker to transfer the NaOH solution to be standardized from its original container to the buret.
2.Student B did not fill the tip of the buret with titrant before starting the NaOH standardization, so the tip contained air when the titration was started, but was filled after the first standardization.
3.Student C over-titrated the php solution, but ignored it and continued on with calculations.
4.Student D was in a hurry to leave the lab. He finished the titration of vinegar without waiting for the pink color to persist for 15 seconds. He recorded the volume of NaOH used, just to notice that the pink color disappeared. He ignored this observation and proceeded with calculations. Students performing vinegar analyses made several mistakes in their experiments. Explain in detail how each error below will affect the final result (% weight of acetic acid in vinegar) of each student's experiment. Show all steps of logic followed in analyzing the effects of the mistake (remember that the experiment had two parts):
1.Student A used a wet beaker to transfer the NaOH solution to be standardized from its original container to the buret.
2.Student B did not fill the tip of the buret with titrant before starting the NaOH standardization, so the tip contained air when the titration was started, but was filled after the first standardization.
3.Student C over-titrated the php solution, but ignored it and continued on with calculations.
4.Student D was in a hurry to leave the lab. He finished the titration of vinegar without waiting for the pink color to persist for 15 seconds. He recorded the volume of NaOH used, just to notice that the pink color disappeared. He ignored this observation and proceeded with calculations. Students performing vinegar analyses made several mistakes in their experiments. Explain in detail how each error below will affect the final result (% weight of acetic acid in vinegar) of each student's experiment. Show all steps of logic followed in analyzing the effects of the mistake (remember that the experiment had two parts):
1.Student A used a wet beaker to transfer the NaOH solution to be standardized from its original container to the buret.
2.Student B did not fill the tip of the buret with titrant before starting the NaOH standardization, so the tip contained air when the titration was started, but was filled after the first standardization.
3.Student C over-titrated the php solution, but ignored it and continued on with calculations.
4.Student D was in a hurry to leave the lab. He finished the titration of vinegar without waiting for the pink color to persist for 15 seconds. He recorded the volume of NaOH used, just to notice that the pink color disappeared. He ignored this observation and proceeded with calculations.
Explanation / Answer
Answer
1. This dilutes the NaOH std. solution and hence a higher wt% of acetic acid results
2. This will show that a higher amount of NaOH is consumed and hence a higher wt.% of acetic acid results.
3. excess amount of php makes it difficult to note the end point and it may appear that the end point (pink color appearence) reached quicker that it actually should, leading to underestimation or a lower wt.% of acetic acid results.
4. this error also results in underestimation of acetic acid as the pink disappears if the end point is not reached.