VITAMIN C EXCRETION PROBLEMSProfessor of Biology and Chemistry University of Cincinnati Clermont College, Batavia OH 45103 |
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rvsd 18 May 1995, 26 March 19961 April 97, 29 Mar 98, 24 Mar 02, 26 Mar 03 |
VITAMIN C EXCRETION PROBLEMSProfessor of Biology and Chemistry University of Cincinnati Clermont College, Batavia OH 45103 |
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rvsd 18 May 1995, 26 March 19961 April 97, 29 Mar 98, 24 Mar 02, 26 Mar 03 |
Remember to set up a table to record and process your titration data
as follows:
aliquot size being titrated:________ mL
conversion factor of iodine being used: _________ mg vitamin C/mL
iodine
| Trial I | Trial II | Trial III | |
| finish: | |||
| start: | _-_________ | _-_________ | _-_________ |
| iodine used: |
The start for trial II should equal the finish of Trial I, etc (assuming no leakage of titrant between titrations). Once the three flasks are titrated, you average the iodine used by adding them up and dividing by three.
The answers to the problems are at the
bottom
of the page.
PROBLEMS:
1. Standardization:
1.00 mL aliquots of 1% ascorbic acid were titrated in triplicate with
iodine of unknown strength. Successive readings on the buret
were:
12.94, 24.35, 35.73, 46.00 mL. What is the conversion factor for
this iodine?
2. Assay of urine:
10 mL aliquots of urine were titrated in triplicate with iodine having
a conversion factor of 0.932 mg vitamin C/mL iodine. The
following
are successive readings on the buret: 15.91, 16.08, 16.28 and
16.47
mL. What is the average amount of vitamin C in the 10 mL aliquot?
3. Assay of orange juice:
5 mL of orange juice was found to contain 2.37 mg of vitamin C.
How much vitamin C is there in 100 mL?
4. Calculation of urine production:
What is the urine production rate per hour if the bladder was voided
at 2:30 and 510 mL was collected at 4:30?
5. Calc. of Vit C excretion rate:
If a person produces urine with 1.43 mg vitamin C/10 mL aliquot, and
they produced 167 mL in an hour, what is the excretion rate/hr?
6. Calculation of urine production:
A person who drank a lot of Coke produced 230 mL in 20 minutes.
What was their urinary production rate per hour?
7. Calculation of urine production:
A person voided after breakfast at 8:27 AM. At 12:15 PM, he
produced
a total of 396 mL of urine. What was his hourly rate of urine
production?
(Hint: express total time as hours, calculating fraction of hr as # of
minutes/60)
8. Calculation of urine production:
A poor A&P student voided her bladder at the beginning of Lab (2:12
PM--she came in late...). At 4:12 PM, she produced 438 mL of
urine.
What is her rate of production of urine per hour?
9. Calc. of Vit C excretion rate:
The student in the previous question titrated 10 mL of urine from
question 8 in triplicate with iodine whose conversion factor was
0.729 mg
vitamin C/mL iodine. She got the following successive numbers:
12.01,
14.79, 17.51 and 20.53 mL.
a: What was the content of vitamin C in 10 mL of her urine?
b. What was the total number of 10 mL aliquots which she produced
in an hour?
c: What was the total amount of vitamin C which she excreted
in an hour?
(Here is problem 9 worked out
if you would like to compare it to your work.)
Answers:
1. 0.907 mg vit C/mL iodine
2. 0.174 mg vit C/10 mL
3. 47.4 mg vit C/100 mL
4. 255 mL/hour
5. 23.9 mg vit C/hr
6. 690 mL/hr
7. 104 mL/hr
8. 219 mL/hr
9a. 2.07 mg vit C/10 mL
9b. 21.9 aliquots
9c. 45.3 mg vit C/hr