Calculations Calculate: 1. the molar concentration of iodate ion, [IO3 -], for e
ID: 969290 • Letter: C
Question
Calculations Calculate:
1. the molar concentration of iodate ion, [IO3 -], for each titration of the filtrate W, then calculate the average [IO3 -].
2. the Ksp based on the average [IO3 -]. Remember that Ksp = 0.5[IO3 - ] 3
3. [IO3 -] in filtrate Ca based on the titration with S2O3 -2.
4. the solubilities of calcium iodate for filtrates W and Ca, in mol/L as well as in mg/mL.
Here is my data:
For Trial 1:
I got 15.9 ml
For Trial 2:
I got 37.9 ml
For Trial 3:
I got 27.8 ml
For Trial 4 (Solution Ca):
I got 18.1 ml
And the exact concentration of sodium thiosulfate is .01M
can you help me do the calculations?
Here is the procedure I was following to get this data:
PROCEDURE
1. a. Place a small amount (no need to weigh) of calcium iodate in a 50 ml beaker containing about 10 ml of distilled water. Swirl gently, you should have a visible amount of undissolved Ca(IO3)2 in the beaker. Label the beaker W. b. Place another small portion of the salt in a second 50 ml beaker (labeled Ca) containing 10 ml of Ca+2 solution (calcium nitrate or chloride will be provided). Let both beakers (W and Ca) stand at room temperature for about 15 minutes, swirling once in a while (3 to 4 times during 15 minute period).
2. Prepare two clean, dry funnels and place a fluted filter paper in each (see the instructions at the end of this document or go to http://www.chem.ubc.ca/courseware/235/danalabsess/flutedfilterpaper.html. Filter solutions W and Ca into two separate dry test tubes (labeled W and Ca, respectively).
3. Wash a burette (if necessary) then rinse it with a small amount (about 5 ml) of sodium thiosulfate solution. Fill it to the 0.0 ml mark with Na2S2O3. Make sure that there are no air bubbles in the tip, and that your burette is not leaking. Record the exact concentration of sodium thiosulfate (displayed on the label).
4. Using a volumetric pipette, transfer exactly 1.0 ml of solution W into a 125 ml Erlenmeyer flask and add 10-15 ml of distilled water. Add 1.0 ml of KI solution followed by 5-6 drops of dilute sulfuric acid. Swirl the flask to mix it then titrate the contents of the flask with sodium thiosulfate until the solution turns pale yellow. Do not over titrate. Add 3-4 drops of starch and finish the titration of the resulting dark navy blue solution (very carefully, using the “drop and swirl” procedure) until the solution is colorless. If there are some dark particles in the colorless solution at the end of titration, continue the titration until they are gone. Record the initial and final volumes in the burette.
5. Repeat step 4 two more time using 2.0 mL of solution W each time.
6. Repeat step 4 using 2.0 mL of solution Ca. Do it once only.)
Explanation / Answer
The net reaction between iodate and thiosulfate:
IO3- (aq) + 6S2O3 2- (aq) + 6H3O+(aq) --------> I- (aq) + 3S4O6 2- (aq) + 9H2O(l)
1 6 6 1 3 9 mole ratio
Ksp of cal iodate =6.47*10^-6
Ksp of sodium thiosulphate =
vol of thiosulphate used molarity of thiosulphate moles of thiosulphate (Molarity* vol in litres) moles of iodate
15.9 .01 .01*15.9/1000 = 1.59*106-4 6*1.59*10^-4 = 9.54*10^-4
37.9 .01 .01*37.9/1000 = 3.79*10^-4 6* 3.79*10^-4 =2.2274*10^-3
27.8 .01 .01* 27.8/1000 = 2.78*10^-4 6* 2.78*10^-4 = 1.668*10^-3
18.1 .01 0.01* 18.1/1000 = 1.81*10^-4 6*1.81*10^-4 = 1.086*10^-3
------------------
average moles 2.78*10^-4
KIO3 > K+ + IO3 -
x x
Ksp = conc of K+ * conc of IO3- = x*x = x^2 = (2.788*10^-4)^2 = 7.773*10^-8
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