Separating mixtures

SEPARATING MIXTURES A review of basic lab techniques PURPOSE: To perform a simple separation and quantitative experiment. MATERIALS: Safety goggles stirring rod 250 mL beaker test tube Bunsen burner wire gauze stand & ring clamp watch glass beaker tongs test tube tongs wash bottle sand/salt mixture 10 and 100 mL grad. cylinder funnel & filter paper 250 mL Erlynmeyer flask marble boiling chip PROCEDURE: 1. TARE a clean, dry 250 mL beaker on the balance. Place about 10 grams of the sand and salt mixture in the beaker. Record the exact mass of the mixture. 2. Record the mass of a piece of filter paper. 3. Record the mass of a test tube and boiling chip (use a small tared beaker as a stand for your test tube). 4. Add about 40 mL of water to the sand/salt mixture (use the beaker to estimate this amount). 5. Assemble the equipment as show by the teacher. Place the wire gauze on the ring clamp and then put the beaker and the mixture on the ring. 6. Light the Bunsen burner following correct procedures. 7. Place the burner under the beaker to be heated (adjust the height of the beaker so that the tip of the flame contacts the bottom of the beaker). Stir the mixture until the water just comes to a light boil. While the beaker is warming, set up the filtering apparatus (place the funnel & filter paper on a 250 mL Erylmeyer flask). Write your initials on the outside of the filter cone in pencil. 8. Pour the contents of the beaker into the filter paper cone using correct filtration technique! Do Not lay stirring rod on the counter - you will lose sample! Use the wash bottle to rinse the beaker and the sand in the filter paper. 9. While the filtrate (salt water) is still dripping label a clean dry large watch glass with your name. 10. When the filtrate is finished dripping through the funnel remove the filter paper carefully and place on the lwatch glass (initials up!). Place in the oven to dry. 11. Swirl the filtrate (the liquid that came through the fiIter paper) well and then pour it into the 100 mL graduated cylinder (or a larger one if necessary). Record the exact volume of the salt water filtrate. DO NOT throw the filtrate away as it will be needed later! 12. Measure out about 10 mL of the filtrate in a 10 mL graduated cylinder. Transfer this to the weighed test tube. Record the exact volume. 13. Relight the Bunsen burner. Holding the test tube with test tube tongs, slowly heat the contents to dryness. When heating a test tube, ensure that the mouth of the test tube is not pointing at yourself or anyone else. 14. When the contents of the test tube are dry (no water droplets visable), turn off the burner and allow the test tube to cool. Determine the mass of the test tube and its contents and record this in your data table. 15. Remove your watch glass and filter paper from the drying oven when the sand is dry. Determine and record the mass of the cool filter paper and sand.. 16. Dispose of the sand by placing it in the container provided by the teacher. Do not pour sand down the sink! Wash all glassware, and return all pieces of equipment to their correct storage locations. DATA: Mass of the sand/salt mixture: __________ g SAND: Mass of filter paper: ______ g SALT: Total volume of all filtrate (salt water): _______ mL Mass of dry sand Mass of empty test tube and filter paper: ______g ________ g and boiling chip Volume of salt water sample CALCULATIONS: heated in test tube: _______ mL Mass of test tube and dry salt: _______ g These must be shown in a logical manner and include the correct units!! 1. Mass of sand in the mixture = (mass of dry filter paper + sand) - (mass of filter paper). 2. Mass of salt in the sample of filtrate = (mass of test tube + salt) - (mass of test tube). 3. Calculate the mass of salt in all of the salt water collected (set-up a simple proportion). 4. Total mass of recovered sand and total salt present in all the salt water. CONCLUSION: Calculate the percent yield of your separation: Mass of separated salt and sand X 100% Original mass of mixture EVALUATION: Comment on your % yield. What could account for it being higher or lower than the mass of the original mixture? How could your procedure have been improved?