Reference no: EM132491625
AMINO ACID TITRATION
Procedure
1. Calibrate the pH meter:
i) Turn the meter to standby.
ii) Plug it in.
iii) Wait about 10 minutes until it warms up.
iv) Adjust the temperature dial to the temperature of the solution.
v) Rinse the electrode with de-ionized (DI) water.
vi) Remove the excess water with a Kimwipe.
vii) Submerge the electrode '/2 inch into a buffer with a pH of 7.
viii) Switch dials on the pH meter to read.
ix) Turn the calibration dial so the meter reads 7.0.
x) Turn the dial back to standby, and remove the electrode from the buffer.
xi) Rinse the electrode with DI water.
xii) Dry it.
xiii) Place it in a buffer solution with a pH of 4.0.
xiv) Re-calibrate the pH meter as with the pH 7.0 buffer.
if your calibration is off, re-do the 7.0 buffer reading, and compromise between the readings for the two buffers.
2. Accurately weigh a .3 g sample of the unknown amino acid into a 150 mL beaker.
3. Dissolve the sample in about 50 mL of DI water. Use enough to cover the electrode tip when it is high enough that the stirring bar doesn't
hit it.
4.1f your amino acid won't dissolve, heat the solution a bit, but then let it cool before titrating.
5. Titrate with standardized .1 M NaOH, using 1 mL increments for the additions.
If a large pH change occurs during titration (>.3 pH), decrease the additions of base to .5 mL or less.
6. Continue the 1 mL incremental additions after the large pH change has passed.
7. Continue the addition of base until the pH reaches a value of 12.5.
8. Draw a graph of the pH vs. mL NaOH added.
9. Calculate the following:
- molar weight,
- pKa, and
- whether the acid is monoprotic, diprotic, or triprotic.
If your molar weight does not match any on the list, then re-do the titration using smaller increments of NaOH around the suspected endpoints.
10. Report the following:
- molar weight,
- pKa, and
- name of amino acid.
2. Choose a flat, level area, if at all possible.
3. place one heavy, triangular block behind each of your rear wheels and in front of your front wheels.
*These blocks will prevent the car from rolling once you have the flat tire jacked into the air.*
set up the jack and loosen the lug nuts
i. Assemble the jack.
*usually you need to insert the handle into a slot on the jack.*
2. Set the jack under the axle and behind the flat tire.
3. Locate the slot on the axle where the jack will engage to lift the flat tire off the ground.
4. Line up the tabs on the top of the jack with the slots on your axle.
5. Wind the jack up until the tabs engage with the axle.
At this point, do not lift the car off the ground.*
6. Using the lug wrench, loosen the four wheel nuts one turn, working in a crosswise pattern around the tire.
Jack up car and remove flat tire
1. Continue raising the jack until the car begins to lift up and the flat tire is well clear of the ground (usually about 8 inches).
*You need to have space under the axle to fit the inflated spare be-tween the car and the ground.*
2. Loosen the wheel nuts the rest of the way.
3. Remove them from the wheel bolts.
4. Place them together on a sheet of plastic or newspaper so that you can easily find them in a few minutes.
5. Remove the flat tire.
Install spare tire
1. Place the spare tire on the axle, lining up the holes with the wheel bolts.
2. Replace the wheel nuts, tightening them finger tight.
3. In crosswise fashion, tighten wheel nuts using wrench.
4. Lower car using jack.
5. Tighten lug nuts as tight as you can, using wrench.
Finishing up
1. Remove jack.
2. Replace jack, lug nut wrench, flat tire, etc. into your trunk.
3. Carefully remove triangular blocks and replace in trunk.
Attachment:- MAS28017 questions.zip