7.03 Lab Ph Essay

Add RO water to the 25 ml volumetric flask up to the mark. Put stopper on the flask and shake it properly.

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.

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

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.

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

2. In Part 1, why did you not observe a stream of bubbles coming off the stainless steel screw in the sugar solution?

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

In this assignment you will be asked to rank aqueous solutions of acids, bases, and salts in order of increasing pH. This is most easily done by first identifying the strong acids that have the lowest pH, the strong bases that have the highest pH, and the neutral solutions that have a pH near 7. The weak acids

4. If the titrated standard NaOH, in the flask against vinegar, in the buret, instead of the way you actually performed the titration, how would you have recognized the end-point with phenolphthalein indicator? Would carrying out the titration in this manner change your calculated results or conclusions?

(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?

4. To utilize the titration results to calculate the molarity of the hydrochloric acid and the

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.

Looking at Figures 2-7, the titration graphs have an interesting curve. The change in pH appears to start slow, then almost instantaneously changes to the neutralized pH. For example, in Figure 2, the olive oil wastewater starts with a very basic pH. As hydrochloric acid is added, the graph appears to slowly move down the Y-axis, meaning the pH is decreasing as well. Suddenly, around the time when about 0.33 units of hydrochloric acid had been added, the graph drops steeply to the acidic pH values and plateaus at the acidic pH of about 1.4. The vegetable oil waste water’s titration curve in Figure 3, the crisco waste water’s titration curve in figure 4, the lard waste water’s titration curve in figure 5, and the detergent I waste water’s titration curve in figure 6 all display the same described pattern as olive oil waste water’s titration curve. In figure 7, the detergent II waste water’s curve follows the same general pattern but is reversed. The graph starts at an acidic pH since the detergent II’s waste water was acidic. Then, it increases slowly at first and exponentially increases in pH with the graph showing a steep curve and eventually leveling out to a basic pH of about 12. The