CHEM 1111 Lecture Notes - Lecture 7: Phenolphthalein, Titration, Antacid

26 views2 pages

lemonfrog498

8 Nov 2014

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Experiment outline: prepare approximately 250 ml of co2-free water by boiling on a hot plate for 5 minutes. Set the boiling water well back from the bench edge: allow the water to cool in a beaker, covered with a watchglass, see tech sections ii. e and f. handle the buret with care as it is quite expensive. A dirty buret can be identified by water drops adhering to the interior walls: if your buret is dirty, remove the stopcock, and using a brush, scrub the buret thoroughly from both ends with soap and water. Your three determinations should not differ by more than 0. 002 m (use equation 3 to do this calculation: use an average of these molarities for analyzing the antacid in the next part of the experiment. Back-titration of an antacid: choose a brand and obtain 2 antacid tablets. Avoid touching them with your fingers as much as possible.

Related Questions

If someone could help me solve the first column of trial #1, I just need to see the steps to solve and then I can finish the rest. Thank you!

The solubility of Borax equal to the number of moles of The number of moles of Borate ions produced in solution is the solubility of solid Borax that dissolved, therefore the concentration of Borate ions is equal to Borax in water. that of borateton Note that the sodium theoquilibrium solution calculate the concentration. By finding the borate ion concentration experimentally you can casily Reaction 2. corresponding sodium ion concentration, and therefore the equilibrium constant for PROCEDURE PREPARATION OF BORAX-BORATE EQUILIBRIUM MIXTURES 1. Room Temperature Solution: Add 3 grams of solid borax, 50 mLofdistilled water and a stir bar to a 100-mL beaker Place on a magnetic stirrer and stir the mixture for at least 15 If minutes. Periodically stop the stirring and make sure there is undissolved borax present. not add some more borax There must be undissolv boraxpresent in order to have 2. equilibrium. Why? a stir Ice Bath Temperature solution: Add 3 grams of solid borax 50 mL of distilled water and a second 100-mL Place this beaker in an ice-water bath and place the bath on magnetic stir for 25-30 minutes. As above, check to make sure there is undissolved stirrer and borax present and add more if necessary. Borate on is weak base o can be titrated with a sandardized hydrochloric acid solution according to Reaction 3 (3) or more simply (4) Note that it requires 2 moles of hydrochloric acid per mole of borate ion for the titration. 3. The HCI solution has been prepared for you by the stockroom. It should be approximately 0.2 M, however, on your data sheet you will need to record the exact molarity of the HCI solution as given on the bottle. 4. Prepare the Buret: Pour approximately 70 to 80 mL of the standard (0.2 M) HCI solu tion into a 250 ml beaker. Record its molarity on your repolt sheet. Clean a 50-mL buret, rinse it with 5-10 mL of HCI solution and let drain. Close the stopcock and fill the buret with the HCI solution. Finding Kspr Titrating Room Temperature Borax with HCI Laboratory 7 l Finding Equilibrium Constants: The solubility of Borax 97

1-How many grams of NaCl would be needed to prepare 150.00 L of a 1.402 M NaCl solution?

............................................................................................................................................................................

2- first a standardized solution of sodium hydroxide (NaOH) will be quantitatively diluted to about 0.1 M but not exactly 0.1M. The molarity of the dilute NaOH will be calculated! A similar quantitative dilution was done in experiment 3 when you diluted 5.0 M HCl to 0.50M HCl using a volumetric flask and pipet.

The second part of the experiment is very similar to the last part of experiment 6 where samples of the unknown were weighed out, dissolved in water, and titrated with the dilute NaOH using phenolphthalein as the indicator to determine the percent by mass of a compound in the unknown. The compound will be different than the compound used in experiment 6. The molecular formula of the compound will be provided during the final. You must know how to weigh by difference (Preweigh, tare sample and small container to zero, transfer sample to flask, and place the small container back on balance to get mass) and titrate the sample using the buret in order to do well.

Be sure to read the instructions for the practical toward the end the CHM151L lab manual and do the practice problem on the next page.

You will have 1.5 hours to do the practical. You may only use a calculator and a pencil on the practical. There is no talking during the practical such that students cannot help each other and the TA may only help you with equipment problems.

It would be a good idea to wash any glassware you might use the lab period before the lab practical. There will also be a help session before the lab practical.

At the end of the lab final you will wash all glassware used or any dirty glassware in your locker, wash your unknown vials and remove the labels, checkin your locker and return your key, and evaluate the lab.

Please put the following statements in the correct order relating to the day of the lab practical:
1 2 3 4 5 6 Wash all your glassware and unknown vials, checkin your locker, evaluate the lab, and check your grades.
1 2 3 4 5 6 Do at least 3 good trials (weigh and titrate sample) as time allows.
1 2 3 4 5 6 Start the lab practical by diluting the NaOH solution.
1 2 3 4 5 6 Before the day of the practical clean glassware, read the practical instructions and do the practice problem in the lab manual and complete the loncapa problems for the final.
1 2 3 4 5 6 Calculate the molarity of the dilute NaOH, the percent by mass of the compound in you unknown for each trial and then the median.
1 2 3 4 5 6 Come to the help session before the lab final.

............................................................................................................................................................................

A NaOH solution was prepared by diluting 5.00 mL of 2.205 M NaOH to a final total volume of 100.00 mL. What is the exact molarity of the dilute NaOH (use 4-5 significant figures)?

............................................................................................................................................................................

4-For the problem above, select glassware and size from the list below to conduct the dilution.

A	Amber Bottle
B	Mohr pipet
C	Buret
D	Volumetric Flask
E	Volumetric Pipet or Pipettor
F	Graduated cylinder
G	Erlenmeyer flask
H	Beaker

A B C D E F G H <= Glassware used to transfer the 2.205 M NaOH to be diluted
A B C D E F G H <= Glassware used to measure the final volume of the diluted M NaOH.

5 10 15 20 25 50 100 250 500 1000 <= Volume of the glassware chosen to transfer the concentrated NaOH above
5 10 15 20 25 50 100 250 500 1000 <= Volume of the glassware chosen to contain the final dilute NaOH above.