mrosales@tenet.edu

To determine the concentration of an unknown nickel (II) sulfate solution by using the colorimeter.

CASIO CFX 9850Ga PLUS, CASIO EA-100, CASIO Lab program, Vernier colorimeter, DIN adapter, five cuvettes, five small test tubes, tissues, stirring rod, 30 ml of 0.40 M NiSO4, 5 ml of NiSO4 unknown solution, two 10 ml pipettes, pipette pump, distilled water, test tube rack, two 100-ml beakers.

1. Wear an apron and goggles. Do not ingest any NiSO4 solution or spill any on your skin.
2. Add about 30 ml of 0.40 M NiSO4 stock solution to a 100- ml beaker. Add about 30 ml of distilled water to another 100- ml beaker.
3. Label four clean, dry, test tubes 1-4. Pipette 2,4,6, and 8ml of 0.40 M NiSO4 solution into test tubes 1-4 respectively. With a second pipette, deliver 8,6,4,and 2 ml of distilled water into test tubes 1-4 respectively. Thoroughly mix each solution with a stirring rod. Clean and dry the stirring rod between stirrings. The fifth test tube will contain the stock solution.
4. Prepare the calculator and the EA-100 for data collection. The calculator and the EA-100 should be linked and the calculator should have the Casio Lab program installed (program can be downloaded from the Casio web page and transferred to the calculator by using the FA -122 program link). Run the Casio Lab program and follow the prompts on the screen.
5. The first task is to calibrate the colorimeter. Prepare a blank by filling a cuvette 3/4 full with distilled water. Wipe clean and dry the cuvette with a tissue and handle the cuvette only by the top edge of the ribbed sides. Place the cuvette (ribbed side away from the light source) in the cuvette slot if the colorimeter and close the lid. Turn the wavelength knob of the colorimeter to the 0%T position. In this position, the light source is turned off, so no light is received by the photocell. When the displayed voltage reading stabilizes, type 0 when the calculator prompts you to. Turn the wavelength knob of the colorimeter to the Red LED position (635nm). In this position, the colorimeter is calibrated to show 100% of the red light being transmitted through the blank cuvette. When the displayed voltage reading stabilizes, type 100 when the calculator prompts you to.
   After recording the A value (slope) and B (y-intercept) value from the calculator screen, place the first cuvette in the colorimeter. Follow the prompts on the calculator screen. Select write (x) and 5 samples when the calculator prompts you. Enter "0.80" into the calculator when it prompts you for the first x value and click the execute button after closing the lid. Wait for the voltage value displayed on the EA -100 to stabilize then press trigger. Record the voltage in the data table. The data pair you just collected should now be in the memory list of your calculator. Take the cuvette out and place aside.
6. Place the second cuvette in the colorimeter. Enter "0.16" into the calculator when it prompts you for the second x value and click the execute button after closing the lid. Wait for the voltage value displayed on the EA-100 to stabilize then press Trigger. Record the voltage in the data table. The second data pair you just collected should now be in the memory list of your calculator. Take the cuvette out and place aside.
7. Repeat procedures for the third cuvette (.24), fourth cuvette (.32), and fifth cuvette (.40). Record the voltage in the data table. When finished with all cuvettes, follow the prompt on the calculator screen.
8. Examine the graph to see if the curve represents a straight line between the variables.
9. Get an "unkown" cuvette. Place it into the colorimeter, and close the lid. Run the program in your calculator one more time. Follow the prompts on the calculator screen. For calibration, enter your A and B value from step 4 instead of running a new calibration.
10. Enter "1" into the calculator when it prompts you and click the execute button after closing the lid. Wait for the voltage value displayed on the EA-100 to stabilize then press trigger. Record the voltage in the data table. Exit the program.
11. Discard the cuvette contents as directed by your teacher.

1. Go to the main menu of your calculator and select the list menu. Type in your x values and y values from your data table.
2. Go to the Stat menu. Select F1 (graph), F1 (graph), F1 (x), Record the a and b values given and then press F6 (draw) to see your graph.
3. Go to the Graph menu. Type in you’re a and b values in y=mx+b form. Press shift F3 (V- Window) and type in your x min and max values as well as your min and max values. Exit, then press F6 (draw).
4. Press shift F5 (G-Solv), F6 (->), F2 (x-Cal), then type in your y value for your unknown to get your x value. Record your x value from the screen on your data sheet. This value is the concentration of your unknown solution.

1 0.08 M ______________

2 0.16 M ______________

3 0.24 M ______________

4 0.32 M ______________

5 0.40 M ______________

UNKNOWN ___ M ______________