experiment 6: Flashcards
Redox titrations involving iodine can be classified into ____ and ____.
iodimetry
iodometry
ascorbic acid or vitamin C is an ____ which plays an important role in ____ the body from disease
antioxidant
protecting
it is not synthesized by the human body, this essential nutrient must be acquired by eating foods rich in Vitamin C
ascorbic acid
Samples containing ascorbic acid can be titrated by ____ in the presence of ____ and ____
potassium iodate
potassium iodide
starch
Iodine is generated by the reaction of iodate with iodide ions.
IO3- + 5I- + 6H+ <—-> 3 I2 + 3 H2O
The iodine produced reacts with ascorbic acid to form dehydroascorbic acid.
C8H8O6 (ascorbic acid) + I2 <—->2I- + C8H6O6 (dehydroascorbic acid)
when all of the ascorbic acid has been consumed, the excess iodine reacts with ____ to form a ____
starch indicator
dark-blue coloration
reagents used
pre-dried standard KIO3
soluble starch
standard ascorbic acid
1.0 M HCI (hydrochloric acid)
0.6 M KI (potassium iodide)
what are the procedure
preparation of standard KIO3 solution
preparation of starch indicator
determintaion of ascorbic acid in commercial fruit juice
how long was the standard KIO3 was dried and in what temperature
several hours at 100 degree Celsius and cooled in a desiccator
weigh how many grams of KIO3 using the analytical balance
0.25 to 0.30g
transfer how many grams of soluble starch in a 100mL clean glass bottle
0.25g
why do wee need to work as quickly as possible when determining of ascorbic acid in commercial fruit juice
as vitamin C is light, air and heat sensitive
what is the diff between iodimetric titrations and iodometric titrations
iodi - involve a reducing analyte. 1 reatcion and a standard soln. of iodine
iodo - involve oxidizing analyt. 2 reaction and a standard soln. of sodium thiosulfate
