Procedure 1. Place the weigh boat on the scale and determine its mass. 2. Add ap

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Procedure 1. Place the weigh boat on the scale and determine its mass.

2. Add approximately 2.0 g of CaCl2 to the weigh boat (the total mass should be the mass of the weigh boat plus 2.0 g). Set this sample aside, and let it sit exposed to the air (but otherwise undisturbed) for 24 hours. Complete Steps 3 - 20 while you wait.

3. Place a 250 mL beaker on the scale. Tare the scale and leave the beaker on the scale.

4. Add approximately 2.0 g. of CaCl2 to the beaker. Record the exact mass of the powder in Table 1.

5. Remove the beaker from the scale. Use a pipette to add 50 mL of distilled water to the beaker and mix with the stir rod until all CaCl2 has dissolved. Note: This is an exothermic process, so the beaker may become warm.

6. Place a 50 mL beaker on the scale. Tare the scale and leave the beaker on the scale.

7. Add 2.5 g of K2CO3. Record the exact mass of the powder in Table 1.

8. Remove the beaker from the scale. Use a pipette to add 25 mL of distilled water to the 50 mL beaker and mix with the stir rod until all K2CO3 has dissolved.

9. Add all of the K2CO3 solution to the beaker containing the CaCl2 solution. It is important that all of the K2CO3 is added. To ensure this, rinse the 50 mL beaker with up to 5 mL distilled water, and pour the rinse in the CaCl2 solution.

10. Stir the solution for approximately four minutes. Then, allow it to sit for 15 minutes. This gives sufficient time for all CaCO3 to precipitate.

11. While the solution is sitting, set up the filtration apparatus. Begin with the ring and a ring stand. Secure the ring to the stand.

12. Place a funnel in the ring, and place a 250 mL Erlenmeyer flask below the ring, such that the bottom of the funnel is also inside the mouth of the flask.

13. Obtain a piece of filter paper. Use the scale to weigh the filter paper and record the mass in Table 1.

14. Obtain a watch glass. Use the scale to weigh the watch glass and record the mass in Table 1.

15. Fold the filter paper in half and in half again, so that it resembles a triangle with one arced side.

16. Pull apart one fold of the filter paper so that three sides of the filter paper remain together, with one side making up the other half of the funnel shape.

17. Place the paper into the funnel and seat with a small amount of distilled water (this will prevent the filter paper from rising up).

18. Filter the solution from the beaker (that you created in Step 9) slowly. Additional distilled water may also be used to transfer any remaining solid into the filtration apparatus.

19. After all the solution has been filtered, use the pipette to rinse the filter paper with approximately 5 mL of isopropyl alcohol to aid the drying process. Allow the isopropyl alcohol to completely drip through the filter before removing filter paper from the funnel.

20. Carefully remove the filter paper, unfold and place it precipitate-side up onto the pre-weighed watch glass. Be sure not to lose any product during this transfer.

21. Repeat Steps 3 - 20 for the CaCl2 that was allowed to sit exposed to air for 24 hours.

22. Allow the products from both trials to dry, undisturbed, for at least 24 hours and determine the mass of the product recovered by re-weighing the system and subtracting the weight of the filter paper and watch glass. Record your data in Table 1.

I ONLY NEED TO DO ONE TRIAL. THE RESULTS IN THE TABLE ARE FROM TRIAL #1.  

Calculations:

1. Theoretical yield of CaCO3 (which is the Mass of Product in the table):

2. Actual yield (CaCO3):

3. Percent yield:

4. Moles of Ca present in original solution, based on actual yield:

5. Mass of CaCl2 present in original solution, based on actual yield:

6. Analyze the data and determine the actual concentration of calcium chloride in the solution. Show all calculations and report in % wt/v concentration.

7. Determine the mass of water which became associated with the calcium chloride during its exposure to the air (I used 50ml of water for the CaCl2 solution. And 25ml of water for the K2CO3 solution).

Table 1: Data and Observations 2 grams before, 2.5 grams after being exposed to air for 24 hours Mass of CaCl2; Mass of K2CO: Mass of Filter Paper Mass of Watch Glass 2.5 grams 2.2 grams 35 grams 1.8 grams 4 minutes Mass of Product Amount of Time Beaker Solution Stirred: Amount of Time Beaker Solution Set: 15 minutes Experimental Observations:

Explanation / Answer

For the given experiment,

CaCl2 + K2CO3 ---> CaCO3 + 2KCl

1. moles of CaCl2 = 2 g/110.98 g/mol = 0.018 mol

moles of K2CO3 = 2.5 g/138.205 g/mol = 0.018 mol

moles of CaCO3 formed = 0.018 mol

theoretical yield of CaCO3 = 0.018 mol x 100.1 g/mol = 1.812 g

2. actual yield of CaCO3 = 1.8 g

3. percent yield = (1.8 g/1.812 g) x 100 = 99.34%

4. moles Ca in original solution based on actual yield = 0.018 mol x 0.9934 = 0.01788 mol

5. mass of CaCl2 present in original solution based on actual yield = 0.01788 mol x 110.98 g/mol = 1.984 g

6. actual CaCl2 in solution (%w/v) = 1.984 g/130 ml = 0.0153%w/v

7. mass of water associated with CaCl2 = 0.5 g per 2.0 g CaCl2

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