SAFE WORK PROCEDURE
LOCATION
VMC
WRITTEN BY: APPROVED BY:
Science Team
Chemical Equilibrium Finding
a Kc Constant
Page 1 of 3
DATE CREATED
WS&H
LAST REVISION
June 27, 2014
New
PERSONAL PROTECTION EQUIPMENT (PPE)
Safety glasses or face shield must be worn at all
times in work areas.
Long and loose hair must be tied back
Appropriate footwear must be worn. Shoe must
be fully enclosed. No open toed shoes.
Close fitting/protective clothing must be worn.
Remove strings hanging from pullovers/sweaters.
Rings and jewelry (long necklaces / bracelets,
etc.) must not be worn.
HAZARDS PRESENT
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Chemical burns
Absorption of Chemicals.
Inhalation of Chemicals.
Ingestion of Chemicals.
Slips / trips & falls
Chemical hazards
ADDITIONAL
REQUIREMENTS
APPARATUS / MATERIALS
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Computer
Vernier computer interface
Logger Pro
Vernier Colorimeter or
Spectrometer
Plastic cuvette
Test tubes
Thermometer
0.002 M KSCN
0.002 M iron nitrate (in 1.0 M
HNO3)
0.200 M iron nitrate (in 1.0 M
HNO3)
Four pipets
Pipet bulb or pipet pump
Beakers
Tissues
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Equipment orientation
WHMIS training
SAFE WORK PROCEDURE
1. Don all personal protective equipment including: safety glasses, & protective nitrile gloves
(where required). Ensure all loose clothing is either removed or tied back. Remove any jewelry
and tie back long hair.
2. Obtain and wear goggles.
3. Label four test tubes 1-4. Pour about 30 ml of 0.002 M iron nitrate into a clean, dry 100 ml
beaker. Pipet 5.0 ml of this solution into each of the four labeled test tubes. Use a pipet pump
or bulb to pipet all solutions. Caution: Iron nitrate solutions in this experiment are prepared
in 1.M HNO3 and should be handled with care. Pour 25 ml of the 0.0020 M KSCN into
another clean, dry 100 ml beaker. Pipet 2, 3, 4, and 5 ml of this solution into Test tubes 1-4,
SAFE WORK PROCEDURE
Chemical Equilibrium Finding
a Kc Constant
Page 2 of 3
respectively. Obtain about 25 ml of distilled water in a 100 ml beaker. Then pipet 3, 2, 1, and 0
ml of distilled water into Test tubes 1-4, respectively, to bring the total volume of each test tube
to 10 ml. Mix each solution thoroughly with a stirring rod. Be sure to clean and dry the stirring
rod after each mixing. Measure and record the temperature of one of the above solutions to
use as the temperature for the equilibrium constant, Kc.
4. Prepare a standard solution of FeSCN2+ by pipetting 18 ml of 0.200 M iron nitrate into a test
tube labeled “5”. Pipet 2 ml of 0.0020 M KSCN into the same test tube. Stir thoroughly.
5. Prepare a blank by filling a cuvette ¾ full with distilled water. To correctly use cuvettes,
remember to wipe the outside of each cuvette with a lint-free tissue, handle cuvettes only by
the top edge of the ribbed sides, dislodge any bubbles by gently tapping the cuvette on a hard
surface, and always position the cuvette so the light passes through the clear sides.
6. Use a USB cable to connect the Spectrometer to the computer. Choose New from the File
menu.
7. To calibrate the Spectrometer, place the blank cuvette into the cuvette slow of the
Spectrometer, choose Calibrate  Spectrometer from the Experiment menu. The calibration
dialog box will display the message: “Waiting 90 seconds for lamp to warm up”. After 90
seconds, the message will change to “Warmup complete.” Click OK.
8. Determine the optimal wavelength for creating the standard curve.
9. Empty the water from the blank cuvette. Using the solution in Test tube 1, rinse the cuvette
twice with ~1 ml amounts and then fill it ¾ full. Wipe the outside with a tissue and place it in the
Spectrometer.
10. Click COLLECT. The absorbance vs. wavelength spectrum will be displayed. Click STOP.
11. To save your graph of absorbance vs. wavelength, select Store Latest Run from the
Experiment menu.
12. Click the configure Spectrometer Data Collection icon on the toolbar. A dialog box will appear.
13. Select Absorbance vs. Concentration under Set collection Mode. The wavelength of maximum
absorbance is automatically identified. Click OK.
14. Leave the cuvette containing the test tube 1 mixture in the device. Close the lid and click
COLLECT. Click KEEP, type 1 in edit box and click OK.
15. Discard the cuvette contents. Rinse the cuvette twice with Test tube 2 solution, fill the cuvette
¾ full and place it in the device. After the reading stabilizes, click KEEP, type 2 in the edit box
and click OK.
16. Repeat the procedure to find the absorbance of solutions in Test tubes 3, 4, and 5.
17. Record the absorbance values for each of the five trials in your data table.
18. Dispose of all solutions as directed.
19. If you have a colorimeter instead of a spectrometer, instead of steps 6-13, perform the
SAFE WORK PROCEDURE
Chemical Equilibrium Finding
a Kc Constant
Page 3 of 3
following:
20. Connect the colorimeter to the computer interface. Prepare the computer for data collection by
opening the file “20 Equilibrium Constant” from the Chemistry with Vernier folder of Logger Pro.
21. Open the Colorimeter lid insert the blank, and close the lid.
22. Calibrate the Colorimeter and prepare to test the standard solutions.
23. Press the < or > button on the Colorimeter to select a wavelength of 470 nm (Blue).
24. Press the CAL button until the red LED begins to flash and then release the CAL button.
25. When the LED stops flashing, the calibration is complete.
26. Empty the water from the blank cuvette. Use the solution in Test Tube 1 to rinse the cuvette
twice with ~1 ml amounts and then fill it ¾ full. Wipe the outside with a tissue and place it in the
colorimeter. Proceed to #14.
27. Clean up your workstation and wash your hands thoroughly.
REGULATORY REQUIREMENTS
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WS&H Act W210, Section 4, 5
Mb. Regulations 217/2006,
Part 16, (Machines / Tools & Robots) Sections 16.1-16.18)
Part 35, (WHMIS Application)
Part 36, (Chemical & Biological Substances Application)