Question

Experiment 1: Gravimetric Analysis with Calcium Chloride and Potassium Carbonate In this experiment, proper analytical experimental techniques will be utilized to perform a double displacement reaction. A solution will be prepared containing a known quantity of calcium chloride. Then, the mass of calcium present will be determined through a careful precipitation of calcium carbonate. You will also investigate the hygroscopic nature of calcium chloride through a comparison reaction. Materials: Scale250 mL Beaker50 mL BeakerStir rod4.0 g Calcium chloride, CaCl25.0 g Potassium carbonate, K2CO3100 mL Graduated CylinderPipetteRing for ring standRing stand Funnel250 mL Erlenmeyer flask2 Filter papersWatch glassWeigh boat*170 mL Distilled water*10 mL Isopropyl alcohol *You must provide Procedure Place the weigh boat on the scale and determine its mass. Add approximately 2.0 g of CaC 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.. Place a 250 mL beaker on the scale. Tare the scale and leave the beaker on the scale.. Add approximately 2.0 g. of CaCl2 to the beaker. Record the exact mass of the powder in Table 1. 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. Place a 50 mL beaker on the scale. Tare the scale and leave the beaker on the scale. Add 2.5 g of K2CO3. Record the exact mass of the powder in Table 1. 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. 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. Stir the solution for approximately four minutes. Then, allow it to sit for 15 minutes. This gives sufficient time for all CaCO3 to precipitate. While the solution is sitting, set up the filtration apparatus. Begin with an iron ring and a ring stand. Secure the ring to the stand. Be sure to select the ring size that most appropriately holds the funnel. 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. Obtain a piece of filter paper. Use the scale to weigh the filter paper and record the mass in Table 1. Obtain a watch glass. Use the scale to weigh the watch glass and record the mass in Table 1. Fold the filter paper in half and in half again, so that it resembles a triangle with one arced side. 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. Place the paper into the funnel and seat with a small amount of distilled water (this will prevent the filter paper from rising up). 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. 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. 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. Repeat Steps 3 - 20 for the CaCl2 that was allowed to sit exposed to air for 24 hours. 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.

Table 1: Data and Observations Substance

Trial 1 Trial 2

Mass of CaCl2: 2g, 2g

Mass of K2CO3: 2.5g, 2.5g

Mass of Filter Paper 1.0g, 1.0g

Mass of Watch Glass 37.9g, 37.9g

Mass of Product 1.6g, 1.4g

Amount of Time Beaker Solution Stirred: 4mins, 4mins

Amount of Time Beaker Solution Set: 15mins, 15mins

Calculations:

First Trial :

Theoretical yield (CaCO3):

Actual yield (CaCO3):

Percent yield:

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

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

Answer 1

Calculations:

First Trial:

Theoretical yield (CaCO₃):

Data: Mass of CaCl₂: 2g Mass of K₂CO₃: 2.5g

Ratio CaCl₂ : K₂CO₃ ---> 1:1

Then, 1 mol of CaCl₂ produce 1 mol of CaCO₃

Theoretical yield (CaCO₃): 1.80g of CaCO₃

Actual yield (CaCO₃): Data: 1.60 g of CaCO₃

Percent yield:

Percent yield: 88.80%

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

Moles of Ca present in original solution, based on actual yield: 0.016 mol of Ca

Mass of CaCl₂present in original solution, based on actual yield:

Mass of CaCl₂ present in original solution, based on actual yield: 1.77g of CaCl₂