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7.03 pH

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by

Oscar Ernand

on 21 October 2014

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Transcript of 7.03 pH

7.03 pH
By Oscar Ernand
Part I: Titration with an Indicator

Fill the 50-milliliter buret with a 0.25 molar NaOH solution.
Record volume.
Measure out between 20 milliliters and 40 milliliters of the unknown HCl solution.
Record volume.
The amount of unknown HCl is then added to the 100-milliliter Erlenmeyer flask.
Add two drops of the indicator, phenolphthalein, to the acid in the flask.
Using the slider on the right hand side, add NaOH to the HCl in the Erlenmeyer flask (This action is known as titrate). Add the indicator until the color of the indicator turns a light shade of pink.
Record the volume.
If you went too far past the end point, please record the results of your trial. Include all sets of data in your lab report.
Part 1 and 2 of Procedure:
Data And Observation Section
"Http://learn.flvs.net/webdav/educator_chemistry_v10/module07/07_03c_a.htm." N.p., n.d. Web.
Resources:
Part II: Titration with a pH Meter

Fill the 50-milliliter buret with a 0.25 molar NaOH solution.
Record volume.
Measure out between 20 milliliters and 40 milliliters of the unknown HCl solution. This amount must be different than the amount used in part I.
Record volume.
The amount of unknown HCl is then added to the 100-milliliter Erlenmeyer flask.
Insert the pH meter into the Erlenmeyer flask and record the initial pH of the acid. Remember to record the pH of the solution after every 5 milliliters of NaOH added.
Titrate the NaOH into the HCl until the buret is empty.
Charts provided by FLVS.Net
Observations:

The color inside of the flask went from being plain clear to a light pink and remained that way regardless.
Calculation and Conclusion
Information Provided by FLVS .net Lesson 7.03ph
Describe the graph of pH values over the course of the reaction in Part II.Was the change in pH consistent over the course of the reaction? Do your best to explain the reason for the shape of the pH curve in your own words?
Ok well with the Acid being HCI and the base is NaOH and just the way my graph shows, when more NaOH is added, it increases, the more we increase the base the less acidic the reaction will be. I hope that explains it well enough.

Why is it important to stir the solution in the flask as you add titrant from the buret?
Because the more you stir the faster the reaction begins to kick in, by stirring you are pushing molecules tighter together.


If a student did not remove all of the bubbles from inside the buret before reading the initial volume and beginning the titration, will this cause the calculated concentration of the hydrochloric acid determined from that trial to be higher or lower than the actual concentration? Explain your answer in complete sentences.
If a student does not remove the bubbles then then the reading of the initial volume would be misread due to their being bubbles causing misreading.

Describe at least three possible sources of error in a titration experiment like this and, for each, explain whether the error would result in a calculated molarity that is too high or too low.
Ok well I think first would be not following thru with accurate data, if you don’t, this could have a bad end result big time. Second I would say is contamination of objects being used in experiment, this could cause a huge impact on the end results. Last I would say is probably using too much NaOH.
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