This is a lab off late nite labs and it called precipitation titration of cobalt

Question

This is a lab off late nite labs and it called precipitation titration of cobalt chloride

Part 1: Perform a Coarse Titration 1. Take a 150 mL Erlenmeyer flask from the Containers shelf and place it onto the workbench. 2. Take the cobalt chloride solution from the Materials shelf and add 10.00 mL to the Erlenmeyer flask. Record this volume in your Lab Notes. 3. Take water from the Materials shelf and add 10 mL to the flask to dilute the solution. This dilution makes it easier to visualize the end point. 4. Take thymolphthalein from the Materials shelf and add 2 drops to the Erlenmeyer flask. 5. Take a burette from the Containers shelf and place it on the workbench. 6. Take 0.100 M sodium hydroxide from the Materials shelf and add 50.00 mL to the burette. Double-click on the burette and select show close up in the Item Properties window to get a closer view of the volume of titrant in the burette. 7. Pass the mouse cursor over the burette and a gray tool tip will briefly display the total volume of NaOH in the burette as well as the volume dispensed. Record these volumes in your Lab Notes. 8. Move the Erlenmeyer flask onto the base of the burette. 9. Click and hold the stopcock for a 1 – 2 seconds. You should observe a rapid stream of drops dispensing from the burette. The volume dispensed should be about 2.00 mL. If the volume dispensed is above 2.50 mL, try holding the stopcock for a shorter period of time. Find the length of time you should click and hold the stopcock to deliver approximately 2.00 mL of titrant. 10. Continue to add titrant in 2.00 mL increments. Pause after each dispensation. Record the dispensed in your Lab Notes. 11. Check if the end point has passed after each dispensation. When the reaction reaches end point the solution changes from pink to blue. 12. Stop adding NaOH once you reach the end point. Record the last burette volume at which the solution in the flask was still pink as well as the volume at which the solution turned blue in your Lab Notes. You now know between which two volumes the end point occurred. 13. Record the volume dispensed before the end point as the final volume in your Lab Notes. 14. Clear your station by dragging your containers to the recycling bin beneath the workbench. Part 2: Perform a Fine Titration 1. Prepare a burette and Erlenmeyer flask as described in steps 1 – 7 in part 1. 2. Add the final volume (before the end point) determined in the coarse titration. To do this, click and hold the stopcock for longer periods of time. The solution in the Erlenmeyer flask should still appear pink. This is near, but not yet at, the titration's end point. 3. Add NaOH one drop at a time. When the solution in the Erlenmeyer flask changes color from pink to blue, stop adding titrant. Record the final volume of titrant dispensed in your Lab Notes. 4. Repeat the fine titration two more times for accuracy, and record the results in your Lab Notes. 5. Clear your station by dragging your containers to the recycling bin beneath the workbench. Remember to press Save Notes.

PLEASE HELP WITH SHORT ANSWER

Short Answer Precipitation Titration of Cobalt Chloride Part 1: Perform a Coarse Titration Lab Results 1.Record the results of your coarse titration in the table below. volume of cobalt (II) chloride titrated (mL) initial volume of NaOH in the burette (mL) dispensed volume of NaOH (mL) Data Analysis 2.What is the volume of NaOH left in the burette at the end of the coarse titration? Part 2: Perform a Fine Titration Lab Results 1.Record the results of your coarse titration in the table below. volume of cobalt (II) chloride titrated (mL) initial volume of NaOH in the burette (mL) dispensed volume of NaOH (mL) Data Analysis 2.What is the average volume of NaOH used in the fine titrations? 3.Calculate the concentration of the cobalt (II) chloride solution titrated in this experiment. Conclusions 1.Suppose you did not have any indicator available, how else would you be able to identify the end point of the titration? 2.Suppose a student found a bottle of sodium chloride solution in the lab without a concentration written on the label. She decided to use a precipitation titration to determine its concentration. Given the data in the table below, what is the concentration of the sodium chloride solution? concentration of AgNO3 solution (mol/L) 0.125 volume of sodium chloride solution (mL) 30.00 volume of AgNO3 dispensed (mL) 24.35

Explanation / Answer

chemical reaction equation,

AgNO3 + NaCl ---> AgCl + NaNO3

1 mole of AgNO3 require 1 mole of NaCl for precipitation of 1 mole of AgCl

moles of AgNO3 = 0.125 M x 24.35 ml

                           = 3.04375 mmol

moles of NaCl needed = 3.04375 mmol

molarity of NaCl solution = 3.04375 mmol/30 ml

                                        = 0.10146 M

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