Experiment 10 - Separation of Components in a Mixture PDF

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Summary

The object of this assignment was to separate the components in a mixture and to create a lab experiment explaining how it can be done so others may be able to perform this experiment as well....

Description

Experiment 10

Separating the Components of a Mixture 520- Group 4 3-21-2018

Experiment 10

Abstract This experiment is designed to help your group become familiar with the methods of separating substances from one another using decantation, extraction, and sublimation. You will then figure out the percentage of the three components in your mixture that you will receive.

Experiment 10

Introduction The matter that most people encounter in their everyday lives consist of mixtures of different substances. Mixtures are two or more substances that retain its own chemical identity thus meaning its own properties as well. Pure substances have a fixed composition, the composition of mixtures can differ. Such as a glass of Texas sweet tea which may contain a little or a ton of added sweetener. The properties or substance that make a mixture are called the components. Homogenous mixtures are mixtures that are uniform in composition, appearance, and properties. Homogenous mixtures are also called solutions; examples are air and a sugarwater solution. Heterogeneous mixtures such don’t have a uniform appearance, composition, or properties. Example of heterogenous mixtures a wood, rocks, soil, and cement. 

Each substance retains its chemical identity in the mixture.

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Mixtures can be separated in to their physical mean by physical means.

If a substance in the mixture is greater than the other substances, then it is called impure. In order to prepare a compound there needs to be an isolation or separation from reactants or impurities. Thus, the purification of impure substances and the separation of mixtures in to their components are common problems. This is seen in every day, drinking water for example is a mixture of silt, sand, dissolved salts, and water. Since water is the largest component in this mixture, it is called impure water. The separation of the components in the mixture is based on the fact that each component has different physical properties. Components of a mixture are called substances, they can be made up of mixture or compounds, and each contain a unique set of properties. The properties in every sample of a substance are identical under conditions of same temperature and pressure. Meaning that once you have determined that a sample of sodium chloride (table salt), NaCl is water soluble and a sample of silicon dioxide (sand), SiO2, is not, you realize that all samples of sodium chloride are watersoluble, and all samples dioxide are not. Likewise, crystals in a pure substance melts at a specific temperature and a given pressure, and boils at a specific temperature and a given pressure.

Experiment 10 Although numerous physical properties can be used to identify a substance, you will be concerned in this experiment merely with the separation of the components and not with their identification. The methods you can use for the separation depend upon the differences in physical properties, and include the following: Decantation- This is the process of separating a liquid from a solid (sediment) by gently pouring the liquid from the solid so as not to disturb the solid. Filtration- This is the process of separating a slid from a liquid by means of a porous substancea filter- which allows the liquid but not the solid to pass through. Common filter materials are paper, layers of charcoal, and sand. Silt and sand can be removed from drinking water by this process. Extraction- This is the separation of a substance from a mixture by preferentially dissolving that substance in a suitable solvent. By this process, a soluble compound is usually separated from an insoluble compound. Sublimation- This is the process in which a solid passes directly to the gaseous state and back to the solid state without the appearance of the liquid state. Not all substances posses to be sublimed. Iodine, naphthalene and ammonium chloride (NH4Cl) are common substances that easily sublime.

Equipment: Balance Watch glass

Tongs

50 or 100 mL graduated cylinder 2 Evaporating dishes

Iron ring

Glass stirring rod

DI water

weighing paper

Safety glasses

Clay triangle or wire gauze

Bunsen burner and hose 2 magnets

Ring stand Ziploc bag

Experiment 10

Goal: To become familiar with the methods of separating substances from one another using decantation, extraction, and sublimation.

Procedure In this experiment you will be working in groups. The mixture you will be separating contains three components: KHP (potassium hydrogen phthalate), Iron fillings, and Sand. Step 1: Obtain 1.00g of the unknown sample from your lab instructor. Your group will then take your evaporating dish and the mixture over to the scale. You will place the evaporating dish on the scale and record the weight on your data sheet. After writing down the weight add about 1 gram of the unknown mixture in the evaporating dish (don’t add more than one gram of mixture). Record the weight of evaporating dish with the mixture. After writing down the weight for the evaporating dish head back to your seat, making sure not to drop the evaporating dish or spilling the mixture. Someone from your group you will need to go and ask the supply room for a plastic Ziploc bag and ask for two magnets in order to separate the iron fillings. Before pouring the mixture into the bag, check for any holes on the bag. A hole will cause you to lose some to all of the mixture and you will have to start over. Once your group has the bag, pour the mixture from the separating dish in to the Ziploc bag. You will then need to carefully place the magnets in the bottom of the bag so that you don’t rip the bag. Once the magnets are in the bag your group may then start shaking the bag gently. Your group should shake the bag thoroughly for about 5 to 8 minutes. Pull the magnets out after the allotted time and place on a weighing paper so you don’t lose any of the iron fillings. If you believe that there is still iron fillings in your mixture your group will need to clean the magnets off and then place them back in the bag and shake for another 5 minutes. Once your group has all of the iron filling out of the sand and KHP mixture you can pour the salt and sand mixture back in to your evaporating dish. Make sure to get all of the mixture out of the bag. Without all of it out of the bag, this will cause an error in the future. Take the evaporating dish with the mixture back over to the scale and weigh it. Record the weight down on your data sheet. To find out how much of the mixture was iron filling you will need to take the initial weight of the evaporation dish and initial mixture and then subtract it by the weight of the evaporation dish and mixture without the iron fillings. Record your answer on

Experiment 10 your data sheet in the spot that says weight of sand. Make sure to include your units of measurement or there will be points subtracted. Step 2: Your group should now have an evaporating dish that contains sand and KHP (potassium hydrogen phthalate). Someone will need to grab your 10-millimeter graduated cylinder and collect 10 millimeters of DI water. After collecting the DI water, you can pour it in to your evaporating dish. From here someone in your group will need someone to stir the mixture and water with a glass stirring road for about 5 minutes. If you believe that there is still KHP floating, you may add a few drops of DI water to fully dissolve the salt. If you put too much water in, it will take longer to evaporate the water later on in the experiment. Step 3: Your salt should now be dissolved in the aqueous solution. Your group will need to grab your other evaporating dish and watch glass to get it ready for the decanting process. Someone will need to weigh the other evaporating dish and watch glass on the scale and record it on the data sheet. To decant, your group will need to have someone place a glass stirring road across the top of your evaporating dish that has the aqueous solution in it, having part of the rod on the pouring spout. Then someone will pick up the evaporating dish and stirring road with a firm grip on top to keep the rod from moving and/or dropping the dish. They will then angle the glass rod over the other evaporating dish and begin to slowly pour the aqueous solution down the glass road in to the other evaporating dish. Make sure to pour the aqueous solution slow to prevent the sand from falling in to the other evaporating dish. If you get sand in the other dish this will cause a small error in your final weight. Make sure to get as much to all of the solution into the other dish or you will still have KHP in the sand. Step 4: Your group should now retrieve a Bunsen burner from your instructor and prepare it for use. After having your lab instructor lite the Bunsen burner place the evaporating dish along with the watch glass and the KHP solution on the clay triangle. You can also use a hot a plate as well. Someone in your group will need to carefully place the evaporating dish along with the watch glass on the heat source to avoid injury. If someone were to get burned report the injury

Experiment 10 immediately to lab instructor. As the solution starts to boil you need to have someone watch the evaporating dish to see when all of the water has evaporated, leaving behind the salt. Look for DI water in the evaporation dish and on the watch glass to be completely evaporated. If there is still DI water, your weight will be off, causing an error. After all of the water has evaporated, someone from the group will need to use a pair of tongs and take the evaporating dish and watch glass of either the clay triangle or hot plate. Place the evaporating dish and the watch glass on someone’s lab book and let it cool. If it is taking a long time to cool, you may run a piece of paper towel under cold water and wrap it around the evaporation dish. Once it is cooled, dry off the outside of the dish. Make sure that both the evaporation dish and watch glass is cooled to room temperature. After the evaporating dish and watch glass have cooled you can cautiously take it over to the scale and weigh it. Record the weight on your data sheet and be sure to include your units of measurements. Once you have the recorded mass of the dish, watch glass and sand, subtract it by the weight of the evaporation dish and watch glass mass to find the mass of KHP. Record the mass of the salt and use appropriate units.

Step 5: You will need to keep your heat source going in order to dry the sand that is in the other evaporating dish. Someone will need to carefully place the evaporating dish with the sand on the heat source to avoid injury. Once the evaporating dish is on the heat source have someone observe the sand until it has dried. Watch to make sure no sand starts popping. Make sure not to take the sand off to early or it will mess with your weight due to DI water still being in the evaporation dish. After the sand has dried someone will need to use a pair of tongs to take the evaporating dish off of the heat source. Turn off the hot plate or Bunsen burner once you are finished drying the sand. Make sure to set the evaporating dish on your lab manual and not directly on the desk. Let the evaporating dish sit and cool till it is almost room temperature. If it is taking too long to dry one may use the cooling procedure explained in step 4. Once it is cooled to room temperature, someone from your group can take the evaporating dish over to the scale and weight it. Record the weight and the units of measurements on your data sheet. Subtract the weight of the evaporation dish from the weight of the evaporation dish with sand. Record the mass of sand in appropriate units. Calculate for percent of each component using the equation:

Experiment 10 % component = mass component/ mass sample in grams x 100% Then use the equation below to show percent recovery of the components: % recovery = (grams of matter recovered/ grams of original sample) x100

Step 6: Once you have recorded the individual masses of the iron fillings, KHP and sand, it is time for proper waste disposal and clean-up of your area, substances and equipment. Check the “Waste Disposal and Cleanup” part of this experiment for the proper way to do so.

Discussion: The most difficult part of this laboratory experiment was removing the iron fillings. We first used the magnets and circled them over the evaporation dish holding the mixture. This took an long time to do with having to stir the mixture and removing the iron fillings, not knowing if all of the iron was out. We were then instructed to retrieve a Ziploc bag, place the mixture and magnets in the bag and shake carefully. This procedure was a lot easier and allowed us to retrieve all of the iron fillings. However, it is still difficult trying to get the iron fillings off of the magnets and onto a weighing paper. To reduce this issue, the next group should weigh the magnets first before placing them in the bag. Thus, the group can subtract that weight from the weight of the magnets with iron fillings, giving the weight of the iron fillings. Our errors came from the Ziploc bag having a hole in the bottom, causing us to lose some off the mixture. Along with the bag, it is not known if all of the sand and KHP mixture is out of the bag and into the evaporating dish. When removing the mixture from the bag, one may spill some onto the table instead of the evaporating dish. Even though the magnet and iron filling procedure was done until there was no more on the magnets after shaking, there could still be some tiny particles left, leaving them in the sand and KHP mixture. When decanting the KHP solution into a different dish, small particles of sand may enter the other dish. If you put too much DI water into the KHP solution, it will take longer for it to evaporate and one may record the mass of the KHP with little bit of DI water still remaining. When weighing, one may not fully

Experiment 10 balance the scale or not waiting for the scale to stop jumping in between numbers. This can cause a big error due to the substances of the mixture weighing less than one gram each, having to equal one gram. One may weigh the hot evaporation dishes too soon, not allowing the evaporation dishes to dry completely, causing an error in the weights. Another error we had was having 116 % recovery. This can be from miscalculations, weighing issues and/or not retrieving all of one component from the rest of the mixture. To avoid these errors, make sure to check the Ziploc bag completely for any holes. If there are holes, you must get a new bag. Try to retrieve all of the mixture out of the bag and into the evaporation, not leaving any in the bag and not spilling onto the table. Use the magnets in the bag multiple times to make sure there is no iron fillings left in the bag. Watch how much DI water you put into the evaporation dish with the sand and KHP mixture. If there’s too much, it will take longer and can lead to errors when evaporating. Pay close attention to the decantation process so no sand enters the KHP and DI water solution. Also, make sure the evaporation dishes and watch glass is cooled to room temperature before weighing. My group believes our goal was almost achieved. We did everything properly and cautiously. However, we did spill some of the mixture out of the Ziploc bag because there was an unknown hole in the bottom. This was one of our errors and what we corrected in our report for the next group to do this experiment. At the end when calculating for the percent recovery, we ended up having 116% which is too much. We believe this is from not retrieving all of the material of one component from the rest. Our experiment was closely related to experiment 2 in our lab. In experiment 2, we used sublimation, decantation and evaporation. These three procedures were also used in my lab groups experiment 10. Due to us already practicing these three procedures for separating a mixture, we had good practice and achieved the goals of each process. During experiment 2, one of our group members learned how to properly decant a solution by placing the glass stirring rod on top. We used this procedure in our own experiment and was very helpful.

Experiment 10

Safety Issues 

Clean up any spills

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Be cautious around the hot plate because it’s hot

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Wash eyes thoroughly if anything gets in them

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If chemicals splash or get on your skin was immediately with soap and water

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If injury occurs inform the lab instructor immediately

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No horseplay is allowed in the lab

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Tie back any long hair

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Don’t wear baggy clothing

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Do not consume any components of the mixture

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Don’t eat food in the lab

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Don’t drink water or any other drink in the lab

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Chewing tobacco or gum is prohibited as well

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Never take off your safety glasses while there are chemicals being used

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Always read the warning labels on chemical you are using

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Never randomly mix chemicals

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Ask your lab instructor if you don’t understand the process

Waste Disposal and Cleanup 

Rinse the evaporating dish with KHP in the sink

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Dispose of the sand and iron filling in to the trash

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Wash all evaporating dishes and watch glasses with DI water and the dry with a paper towel

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Check all equipment for cracks and damage before leaving the lab

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Make sure you put all equipment away before leaving the lab...