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Iodide Oxidation by Hydrogen Peroxide

by buzzingbee
Tags: hydrogen, iodide, oxidation, peroxide
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buzzingbee
#1
Feb27-13, 03:45 PM
P: 3
In my chemistry lab we prepared the following solutions:
Buffered Iodide Solution
25 mL acetic acid/sodium acetate buffer
6mL of 0.5 % starch solution
6 mL of 1.0M KI
fill to the 250 mL mark with distilled water

0.025M Thiosulfate Solution
5 ml of 1 M Na2S2O3
fill to the 200 ml mark with distilled water

Peroxide Soution
30ml of 1 M H2O2
fill to the 150 ml mark with distilled water

Then mixing these solutions together:
Mixture 1:
Buffered Iodide 40ml
Thiosulfate Solution 10ml
Distilled Water 10 ml

Mixture 2:
Buffered Iodide 40ml
Thiosulfate Solution 10ml
Distilled Water 20ml

Mixture3:
Buffered Iodide 40ml
Thiosulfate Solution 10ml

Mixture 4:
Buffered Iodide 40ml
Thiosulfate Solution 5 ml
Distilled Water 5ml

Separately put each beaker into ice water and measure the following amounts of peroxide solution separately into the container of ice:
Mixture 1: 20ml
Mixture 2: 10ml
Mixture 3: 30ml
Mixture 4: 30ml
when the two flasks have cooled on ice below 3C add the peroxide
time as soon as you add peroxide into the flask

I am unsure for my lab questions what values to use for each trial to calculate the moles of sodium thiosulfate reacted? and how to calculate the mol/L H2O2 reacted
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chemisttree
#2
Feb27-13, 04:58 PM
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Strangest lab I've ever seen.
Borek
#3
Feb28-13, 02:14 AM
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P: 23,536
Quote Quote by buzzingbee View Post
0.025M Thiosulfate Solution
5 ml of 1 M Na2S2O3
fill to the 200 ml mark with distilled water
How many moles of thiosulfate in 5 mL of 1M solution?

What is the concentration of solution that contains this number of moles of thiosulfate in 200 mL?

buzzingbee
#4
Feb28-13, 02:45 AM
P: 3
Iodide Oxidation by Hydrogen Peroxide

wouldn't the concentration be 1 M
Borek
#5
Feb28-13, 03:14 AM
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P: 23,536
No. Don't guess, try to calculate, following exactly questions as I listed them. This is mostly a simple plug and chug - use the definition of the concentration rearranged to isolate thing that you want to calculate.


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