Experiment_603_Separating Components of a Mixture 1_4_3

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Student Name

Laboratory Date:

Date Report Submitted:

___________________________

Student ID

Experiment Number and Title

Experiment 603: Separating Components of a Mixture

Experiment 603: Separating Components of a Mixture

Section 1: Purpose and Summary

Learn how to separate components of a mixture.
Calculate the percent composition of a mixture.
Calculate percent recovery of sample.

In this experiment, students will separate the components of a mixture containing sand (mostly SiO₂), table salt (NaCl), and calcium carbonate (CaCO_³). Students will perform various separation techniques such as dissolution, filtration, decantation, and evaporation to isolate each component of the mixture. Students will learn how to calculate the mass of recovered component after each separation and the determine percent recovery of a sample.

Section 2: Safety Precautions and Waste Disposal

Safety Precautions:

Hydrochloric acid (HCl) is corrosive and toxic. Avoid contact with your eyes, skin, and clothing.

Handle hot glassware with tongs.

Do not place hot glassware on cold or wet surfaces. The thermal shock can break glass and porcelain.

Use of eye protection is required for all experimental procedures.

Waste Disposal:

Collect all recovered materials in a designated waste beaker.

Section 3: Procedure

NOTE: Time management is extremely important to be able to successfully complete this experiment within one laboratory period. Use the following flow chart:

Part 1: Preparation of the sample mixture

1. Obtain an unknown sample from the stockroom window. Record the unknown sample number.

Unknown sample number:

2. Weigh a clean and dry 100-mL beaker (Beaker #1).

Mass of Beaker #1:

(a) __________________grams

3. Transfer approximately 3 grams of unknown sample into Beaker #1. Record the exact mass to the nearest centigram (two decimal places).

Mass of Beaker #1 with unknown sample:

(b) __________________grams

Part 2: Extraction of NaCl

1. To the sample, add approximately 50 mL of laboratory water and stir continuously with a glass stirring rod for about two minutes. Let mixture stand for a few minutes to allow the undissolved components settle to the bottom of the mixture.
2. Weigh a clean and dry 250-mL beaker (Beaker #2). Record exact mass.	Mass of Beaker #2: (c) __________________grams
3. Weigh a clean and dry ceramic evaporating dish. Record exact mass.	Mass of evaporating dish: (d) __________________grams
$\\lmcpitpfs1.lmc.local\homedirs\pwest644\Documents\A_ZeroCostTextbooks\Chem_6_Rewrite_2018\In Process Experiments\Photos\filterphoto11.jpg$ 4. Prepare a vacuum filtration set up: a) You will need a Buchner funnel, a clean 250-mL vacuum filter flask, a filter adaptor (often a one-hole stopper), a pre-cut filter paper and Beaker #2. b) Place the filter paper on the Buchner funnel. The filter paper should fit snugly and cover all the small holes in the funnel. c) Using the filter adaptor, place the Buchner funnel on top of a vacuum filter flask. You might need to use a clamp and a ring-stand to keep the setup intact and upright. d) Connect a vacuum tubing hose to the vacuum filter flask and to the vacuum supply. e) Wet the filter paper with a little laboratory water. Turn the vacuum on and confirm that there are no leaks.
5. While the vacuum is engaged, carefully pour the water/sample mixture into the funnel. Transfer all the residue into the funnel. Use some laboratory water if necessary, to transfer the residue.
6. Gather the filter paper from the funnel using the edge of the filter paper. You might need to use tweezers. Avoid losing any solids. Save the solids and the filter paper in the pre-weighed evaporating dish for Part 3.
7. You need to transfer all the filtrate from the vacuum filter flask to another container to evaporate it to dryness. This is called a quantitative transfer. Pour the filtrate from the vacuum filter flask into Beaker #2. Using a minimal amount of laboratory water, rinse the inside of the vacuum filter flask into Beaker #2. Three good rinses is usually sufficient.
$\\lmcpitpfs1.lmc.local\homedirs\pwest644\Documents\A_ZeroCostTextbooks\Chem_6_Rewrite_2018\In Process Experiments\Photos\beakerphoto12.jpg$ 8. Begin the evaporation of the solution in Beaker #2 on a hot plate. Do not evaporate to dryness on the hot plate. You will have better control of the final evaporation by using a Bunsen burner setup.
9. When sample in Beaker #2 is almost dry, place Beaker #2 on a wire mesh and ring stand over a Bunsen burner. Heat the solution in Beaker #2 on a Bunsen burner and evaporate to dryness. As the solution approaches dryness, it may sputter if it is heated too fast. Avoid loss of product by finishing this final evaporation step slowly.
10. After the sample has evaporated to dryness, allow Beaker #2 to cool and weigh. Record exact mass.	Mass of Beaker #2 with residue (NaCl): (e) __________________grams
11. Wash, rinse, and dry Beakers #1 and #2.

Part 3: Separation and recovery of sand

1. Using a spatula, completely transfer the residue from the filter paper into the pre-weighed evaporating dish. Wash the filter paper with a few drops of laboratory water to complete the transfer. When you are satisfied that no solids remain on the filter paper, discard the filter paper.
2. To this mixture of solid sample and water, slowly add about 8 mL of 3 molar (M) hydrochloric acid (HCl) solution. Stir the mixture continuously until the bubbling disappears. Let the mixture stand for a few minutes to settle.
3. Decant the supernatant into a 400-mL beaker, collecting as much liquid as you can. Avoid transferring any remaining solids from the evaporating dish. Wash the residue in the evaporating dish with approximately 5 mL of laboratory water; allow the residue to settle and decant again. Do the washing and decanting steps two times, collecting all liquid into the 400-mL beaker. Avoid transferring any solid material to the beaker.
4. After the last washing is completed, set aside the liquid in the 400-mL beaker for Part 4 of this experiment.
$\\lmcpitpfs1.lmc.local\homedirs\pwest644\Documents\A_ZeroCostTextbooks\Chem_6_Rewrite_2018\In Process Experiments\Photos\dishphoto10.jpg$ 5. Set up a Bunsen burner with a wire screen on a ring stand with an iron ring. Place the evaporating dish on the wire screen and use the Bunsen burner to drive off all moisture from the residue. Evaporate any liquid until the residue on the evaporating dish is dry.
6. Cool the evaporating dish and weigh. Record exact mass.	Mass of evaporating dish with residue (sand): (f) __________________grams
7. Discard sand into the garbage can, NOT in the sink.

Part 4: Extraction of CaCO₃

1. Using a hot plate, evaporate the solution in the 400-mL beaker to boiling. Continue boiling for 5 minutes or until about half of the volume of the solution remains.
2. Using tongs, remove the 400-mL beaker from the hot plate. Let it rest on a wire gauze on the bench top and immediately add about 15 mL of 1 M K₂CO₃ solution. Stir the mixture for about 5 minutes, then allow it to cool to room temperature. This delay allows small microcrystals to become larger, which makes it possible to filter them.
3. Meanwhile, obtain another pre-cut filter paper and a clean, dry watch glass. Put the filter paper on the watch glass and weigh. Record exact mass.	Mass of watch glass and filter paper: (g) _________________grams
4. Prepare a vacuum filtration set up, as described in Part 2 of this experiment. Use the pre-weighed filter paper above (step 3).
5. Carefully pour the reaction mixture into the Buchner funnel. Transfer all the residue (CaCO₃) into the funnel using a stream of laboratory water from a wash bottle.
6. After filtration is done, discard filtrate into the drain. Remove the filter paper containing CaCO₃ and place it on the pre-weighed watch glass.
7. Place the filter paper and CaCO₃ on the watch glass in an oven to dry completely. If the oven temperature is at 100 °C, this should take around 15 minutes. Be careful to use tongs to remove the watch glass from the oven. It will be hot! Alternatively, your instructor may allow you to let your CaCO₃ air dry and weigh it during the next laboratory period.
8. If you used the oven method for drying, let the watch glass cool to room temperature. Weigh the dried CaCO₃, filter paper and watch glass. Record exact mass.	Mass of watch glass, filter paper, and CaCO₃: (h) __________________grams
9. Discard filter paper and residue into the garbage can in the lab.

Section 4: Calculations

From the masses you recorded in Part 1 of this experiment, calculate the mass of your unknown sample mixture.

(b) – (a)

Total sample mixture (by difference)

(i) _________________ g

From the masses you recorded in Part 2 of this experiment, calculate the mass of NaCl extracted.

(e) – (c)

(j) _________________ g NaCl

From the masses you recorded in Part 3 of this experiment, calculate the mass of sand recovered.

(f) – (d)

(k) ________________ g sand

From the masses you recorded in Part 4 of this experiment, calculate the mass of CaCO3 extracted.

(h) – (g)

(l) _______________ g CaCO₃

Calculate % NaCl recovered by dividing the mass of NaCl extracted (j) by the mass of your unknown sample mixture (i). Express the fraction as a percentage (multiply by 100).

(m) _______________ % NaCl

Calculate % sand recovered by dividing the mass of sand recovered (k) by the mass of your unknown sample mixture (i) Express the fraction as a percentage (multiply by 100).

(n) ________________% sand

Calculate % CaCO₃ recovered by dividing the mass of CaCO₃ extracted (l) by the mass of your unknown sample mixture (i). Express the fraction as a percentage (multiply by 100).

(o) _______________% CaCO₃

Calculate total mass of components recovered by adding the mass of recovered NaCl (j), recovered sand (k) and recovered CaCO₃ (l).

(p) ________________ g NaCl + sand + CaCO₃ recovered

Calculate % recovery by dividing the total mass (p) by the mass of your unknown sample mixture (i). Express the fraction as a percentage (multiply by 100).

(q) _____________ % recovery

Post-Lab Questions:

1. In Part 3 Step 3, after decanting the supernatant into the beaker, the residue (sand) was washed a few times with laboratory water. Explain why this washing step is necessary.

2. Obtain the actual percentage of each component in your unknown mixture from your instructor. Compare the values and explain why your calculated percentages are higher or lower than the actual values. What may have caused the error?

3. Student Fumblefingers did the experiment but did not evaporate the NaCl to complete dryness. What is the effect on the following calculated values?

a) % NaCl

b) % recovery

4. The calcium carbonate was reacted with hydrochloric acid to separate it from the sand. A partial chemical equation for this reaction is listed below:

CaCO₃(s) + 2 HCl (_aq) → Ca⁺²(_aq) + 2 Cl^-(_aq) + H₂O + something

Note: The subscript “(_s)” means solid. The subscript “(_aq)” means aqueous or dissolved in a solution.

a) What do you think “something” might be? Would the generation of “something” be consistent with your observations?

b) Now that you have an idea of what “something” is, write out the fully balanced chemical equation for the reaction in Part 4.

Notes: