Question

Procedures

1. Place two 150 mL Erlenmeyer flasks from the Containers shelf on the workbench. Double-click on the flasks to label one flask “A” and the other “B”. Obtain a 10 mL graduated cylinder and a 50 mL graduated cylinder from the Containers shelf.

2. Place two constant temperature baths from the Instruments shelf onto the workbench.  

3. Set the temperature on each bath to 21.5 °C.

4. The contents of each flask will vary with each trial as indicated in the table below.

   Flask contents
   	Flask A			Flask B
   Trial	Volume of 0.2 M Potassium Iodide (mL)	Volume of 0.2 M Potassium Nitrate (mL)	Volume of 0.2% starch (mL)	Volume of 0.2 M Ammonium Persulfate (mL)	Volume of 0.2 M Ammonium Sulfate (mL)	Volume of 0.01 M Sodium Thiosulfate (mL)
   Trial 1	25	0	5	25	0	10
   Trial 2	25	0	5	12.5	12.5	10
   Trial 3	25	0	5	6.25	18.75	10
   Trial 4	12.5	12.5	5	25	0	10
   Trial 5	6.25	18.75	5	25	0	10

   5. For trial 1, measure the indicated volume of each reagent from the Materials shelf using the appropriate graduated cylinder, then add to the flask.

   6. Record the color of the initial solutions.

   7. Move each flask into a water bath.

   8. Pour the contents of flask B into flask A. Immediately note the time, including seconds, from the laboratory clock or other timing device.

   9. Note the time elapsed when the color changes from clear to black. Record the time.

   10. Discard all materials in the waste, then place the containers in the sink.

   11. Repeat steps 1 – 10 for trials 2 – 5.

   12. Clear the bench of all materials, containers, and instruments, then return to your course page to complete any assignments for this lab.
   
   
   
   
   
   
   
   
   
   
   My question is what is the goal and purpose for this lab experiment ? please state the goal.

Answer 1

Solution:

The Reaction done in this Experiment is the Iodine-Clock Reaction.

The Goals and Purposes of this Experiment are as follows:

a) To Determine the Amount of Free Iodine from the KI required to react with 5ml of 0.2% Starch to Produce a Colour Change from Clear to Blackish Blue Solution.

b) To Determine the Time required for the Reaction of Free Iodine with Starch to give the Colour Change.

c) To Determine the Amount or Concentration of KI required to react with the Starch to form a Iodide- Starch Complex.

d) To find the Limiting Reagent in the Reaction and to compensate for that by Increasing the Volume of the Reagent keepiy the Concentration Same.

e) To Determine the Anount of Ammonium Persulphate which Reacts with Iodide Ions from KI to Produce Sufficient amount of Iodine which can Complex with the Starch and give a Colour Change.

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