7.03 Lab Ph Essay

We know that that the end point of the titration is reached when, after drop after careful drop of NaOH, the solution in the flask retains its pale pink color while swirling for about 30

12) [3.4] Does your graph show evidence for biomagnification of mercury in this lake? Explain in 4-5 sentences. (4pts)

1. Record your hypothesis about what will happen when Biuret solution is mixed with the solutions from test tubes 1, 2, 3, and 4 here. Be sure to use scientific reasoning to support your hypothesis.

2. To titrate a hydrochloric acid solution of “known” concentration with standardized 0.5M sodium hydroxide.

Keep adding five drops of HCl or the solution until a total of thirty drops have been added.

pH was recorded every time 1.00 mL of NaOH was added to beaker. When the amount of NaOH added to the beaker was about 5.00 mL away from the expected end point, NaOH was added very slowly. Approximately 0.20 mL of NaOH was added until the pH made a jump. The pH was recorded until it reached ~12. This was repeated two more times. The pKa of each trial are determined using the graphs made on excel.

1. Develop hypotheses predicting the effect of pyrite and coal on the acidity of water?

mL cylinder to the beaker on the stir plate and empty it into the beaker. Place the pH probe in the beaker and record the pH in the data table. Drag the beaker to the red disposal bucket. Double-click the bottle of NaHCO3 to move it to the Stockroom counter. Repeat steps 5 and 6 for KNO3.

After the twenty minutes elapsed, the flask was cooled to room temperature and then titrated with the remaining NaOH until the colorless solution remained pink. The final volume was then recorded. While solution #1 was heating the same process was repeated with solution#2 and the second burette

Before beginning an experiment, it is good to calibrate any equipment that needs calibration. This ensures that results obtain will be as accurate as possible or as near to the true value. All equipment should be inspected to ensure that there are no chips, cracks or general damage to the equipment as these could cause problems during the experiment which could affect the overall results gained. Equipment such as burettes, pipettes, flasks and beakers must be rinsed with distilled water to get rid of any impurities in the equipment. If solutions are to be poured in any piece of equipment then the equipment should also be rinsed out with the solution being used, this will maintain the pH level in the instrument. Once a solution is transferred from the pipette to the flask, touching the tip of the pipette on the side of the flask will drain any extra drops that may still remain on the tip of the pipette.

ii. The second part of the titration series involves titration of NaOH with Hydrochloric acid (HCL). Again, three reps of titration and a blank titration have to be completed. A volumetric pipet is used to measure 10.00mL of HCL into three labeled conical flasks. Then the flasks are filled with deionized water until about the 50mL mark. A buret is

(b) Why are air bubbles in the buret tip a possible source of error in a titration experiment? How do you remove air bubbles from the buret tip?

5. Why is it a good idea to rinse the buret with the NaOH solution, instead of with water, before filling it at start of the titration?

A 1M concentration of each was used in the titrations when a 6 M concentration should have been used. As a result, this caused the calculated concentrations of the wastewater to be higher than they otherwise would be.

For the titration of acetic acid 2mL of acetic acid solution was measured and put inside of the Erlenmeyer flask. The acetic acid was then diluted with 50mL of distilled water. Three drops of phenolphthalein indicator were then added to the acetic acid solution. Then, the titrant (sodium hydroxide solution) in the buret was added into the Erlenmeyer flask very slowly until the solution reached the equivalence point. At the endpoint when the solution turned pink the stopcock was closed and the Volume was recorded. The Erlenmeyer flask was cleaned, the buret was refilled with the titrant, and the experiment was repeated again.