Would the following procedural errors result in an incorrectly high or low calculated percent NaOCl in commercial bleach solution?
A student failed to allow the volumetric pipet to drain completely when transferring the diluted bleaching solution to the Erlenmeyer flask. I get incorrectly low.
A student blew the last drops of solution from the pipet into the volumetric flask when transferring commercial bleaching solution to the flask. I get no effect.
A student began a titration with an air bubble in the buret tip. The bubble came out of the tip after 5 mL of Na2S2O3 solution had been released. I get incorrectly high.
Are these correct because this kind of question confuses me. Thank you!
Yes, these answers are correct. In the first case, the student would have transferred less solution than intended, resulting in a lower calculated percent NaOCl. In the third case, the air bubble would have caused the student to add more Na2S2O3 solution than intended, resulting in a higher calculated percent NaOCl.
Yes, your answers are correct! Let me explain why each procedural error would result in an incorrectly high or low calculated percent NaOCl in the commercial bleach solution:
1. When the student failed to allow the volumetric pipet to drain completely, it means that not all of the diluted bleaching solution was transferred to the Erlenmeyer flask. As a result, the amount of NaOCl in the solution would be underestimated, leading to an incorrectly low calculated percent NaOCl.
2. Blowing the last drops of solution from the pipet into the volumetric flask does not significantly impact the accuracy of the results. Since the last drops blown into the flask would not change the overall concentration of NaOCl in the solution, there would be no effect on the calculated percent NaOCl.
3. Starting a titration with an air bubble in the buret tip can lead to an incorrectly high calculated percent NaOCl. This is because the initial volume of Na2S2O3 solution released from the buret includes the volume occupied by the air bubble. As the titration proceeds and the bubble comes out, it gives the impression of a higher volume of Na2S2O3 solution used, causing an overestimation of the amount of NaOCl in the bleach solution and leading to an incorrectly high calculated percent NaOCl.
It's great that you asked for clarification. Understanding these procedural errors is important to ensure accurate results in experiments.
Yes, your answers are correct. Let me explain each scenario in more detail:
1. The student failed to allow the volumetric pipet to drain completely when transferring the diluted bleaching solution to the Erlenmeyer flask. This would result in an incorrectly low calculated percent NaOCl. By not allowing the pipet to drain completely, the student would have transferred less solution than intended into the flask, leading to a lower concentration of NaOCl.
2. The student blew the last drops of solution from the pipet into the volumetric flask when transferring commercial bleaching solution. In this case, there would be no significant effect on the calculated percent NaOCl. Blowing the last few drops of solution into the flask would not significantly alter the volume or concentration, and therefore would not lead to an incorrect result.
3. The student began a titration with an air bubble in the buret tip, which then came out after releasing 5 mL of Na2S2O3 solution. This would result in an incorrectly high calculated percent NaOCl. When the air bubble comes out, additional Na2S2O3 solution will be added to the reaction, potentially leading to an excess of Na2S2O3 being used in the titration. The excess Na2S2O3 would falsely increase the apparent concentration of NaOCl and result in an overestimation of the percent NaOCl in the bleach.
So, in summary, failing to allow the pipet to drain completely would result in an incorrectly low value, while starting a titration with an air bubble would give an incorrectly high value for the calculated percent NaOCl. Blowing the last drops of solution from the pipet would have no significant effect on the calculated result.