Illustrated Guide to Home Chemistry Experiments

358 DIY Science: Illustrated Guide to Home Chemistry Experiments

TABLE 20-1: Quantitative analysis of vitamin C by acid-base titration—observed and calculated data

Item value

A. Mass of empty 125 mL Erlenmeyer flask __________. ____ g

B. Mass of empty 125 mL flask + vitamin C table __________. ____ g

C. Mass of vitamin C table (B – A) __________. ____ g

D. Initial volume of sodium hydroxide titrant ______._____ mL

E. Final volume of sodium hydroxide titrant ______._____ mL

F. Volume of sodium hydroxide titrant used (C – B) ______._____ mL

G. Moles of sodium hydroxide required to reach endpoint ___.________ mol

H. Mass of ascorbic acid present in the sample __________. ____ g

oALIpToN ACTIvITIES

If you have time and the required materials, consider performing these optional activities:

• Repeat the experiment, using the same unknown and titrant, and compare the result of
  your second titration with that of the first. Repeat again as necessary until you have at
  least two titrations whose results are closely matched.


• Repeat the experiment, using a 10.00 mL aliquot of lemon juice concentrate (assume
  that all acid present in the sample is ascorbic acid).


• Repeat the experiment, using a 100.0 mL aliquot of orange juice.


• Reproduce the experiment that Dr. Mary Chervenak describes in her comments above.

dISoALp S :

The waste solutions

from this lab can be

flushed down the drain

with plenty of water.

SBSTITUTIU oNS ANd modIfICATIoNS

• You may substitute any suitable container of similar
  size for the 125 mL Erlenmeyer flask.


• The 0.1000 M sodium hydroxide solution should
  be standardized, if possible. (You can standardize
  it against the hydrochloric acid you standardized
  in chapter 11. If you do not have standardized
  sodium hydroxide available, you can make do with
  a nonstandardized solution of 4.00 g of sodium
  hydroxide dissolved in water and made up to 100.0 mL
  in a volumetric flask.

dAR. Rm y CHERvENAk CommENTS:

An introductory biology class that I took had students

consume a known amount of Vitamin C and then collect

urine for the 24-hour period following consumption.

The urine was then analyzed for Vitamin C. It really was

astonishing how little Vitamin C was actually absorbed.

Easily one of my favorite experiments.