The Purpose: purpose of this experiment is to observe the solubility of substances in water, measure the effect of various factors on solubility rate, prepare a supersaturated solution, and observe how water reacts as a reaction medium. Procedure: Materials needed: 250-mL beaker Iron ring Hot plate 8 small-sized test tubes Test tube rack Sodium sulfate (irritant, hygroscopic) Barium sulfate Finely ground sucrose Naphthalene (flammable, suspected carcinogen) Urea (irritant) Stirring rod 6 medium-sized test tubes Graduated cylinder Sodium thiosulfate Sodium hydrogen carbonate Citric acid Ethanol (flammable, toxic) Vegetable oil Glycerol (irritant, hygroscopic)
1. Prepare a boiling water bath, filling a 250-mL beaker with hop tap water and placing a ring support around the beaker for stability. Heat using a hot plate. 2. Obtain 8 small-sized test tubes and place in test tube rack. 3. Transfer 1 mL of distilled water to each tube using a graduated cylinder. Then add the following to the labeled tubes: Tube 1: sodium sulfate Tube 2: barium sulfate Tube 3: finely ground sucrose Tube 4: naphthalene Tube 5: urea Tube 6: ethanol Tube 7: vegetable oil Tube 8: glycerol 4. Thoroughly mix contents of each tube and record observations of each solution/ 5. Discard contents 2, 4, and 7 in labeled containers. Pour contents 1, 3, 5, 6, and 8 down drain. 6. Assemble 6 clean, dry, small test tubes labeled 1-6. 7. Transfer 5 mL of distilled water into each tube. Place tubes 3-6 in boiling-water bath. 8. Testing one tube at a time, add solutes below to the tubes. Determine time it takes for sucrose to dissolve. Begin to time each system as soon as you add the sucrose. Stir contents of tubes 2 and 4, but do not stir contents of tubes 1, 3, 5, and 6. Tube 1: lump sucrose, unstirred, room temperature Tube 2: lump sucrose, stirred, room temperature Tube 3: lump sucrose, unstirred, heated Tube 4: finely ground sucrose, unstirred, room temperature Tube 5: finely ground sucrose, unstirred, room temperature Tube 6: finely ground sucrose, unstirred, heated
9. Pour contents of tubes 1-6 in drain. 10. Weigh 4 g of sodium hyposulfite. Place in clean, dry, medium-sized test tube. Add 1 mL of distilled water and mix well. Record observations. 11. Place test tube containing sodium thiosulfate solution into your boiling-water bath for 5 min. Mix well during heating. Record observations after 5 min. 12. Allow test tube to sit undisturbed and cool to room temperature. 13. After the test tube has cooled, record observations. 14. Without disturbing test tube, add a sodium thiosulfate crystal the size of a small pea to the test tube containing the sodium thiosulfate solution. Allow the tube to sit undisturbed and observe for 3 min. Record observations. 15. Pour the contents of test tube into labeled container. 16. In a clean, dry, small-sized test tube, place pea-size samples of solid, dry sodium hydrogen carbonate and solid, dry citric acid. Mix thoroughly. Record observations. 17. Slowly add 1 mL of distilled water to the test tube, carefully observing the contents during addition. Record observations. 18. Stir and record observations. 19. Pour your reaction mixture into the drain. 20. Wash test tubes with soap or detergent, rinse with tap water then distilled water. Data: Part 2 Observations: Sodium sulfate (Na2SO4) was insoluble in water for this experiment. It is an ionic compound that, when mixed with water, does not dissolve. Instead, sodium sulfate stuck to the bottom of the tube and proved to be insoluble. Barium sulfate (BaSO4) is also an insoluble ionic compound. When mixed with water, it became a thick, pasty, cloudy solution. Sucrose (C12H22O11) is a soluble compound that is covalent. When I mixed sucrose in water for this experiment, the solution was clear and proved to be soluble. Naphthalene (C10H8) has an ionic-type bond. In experiment, the naphthalene was insoluble because when I added it to water, there were chunks floated on the top and fell to the bottom. They did not mix with water. Urea (CH4N2O) is a soluble, covalent compound. When added to water in the experiment, it dissolved, and had a slightly yellow, discolored appearance. Ethanol (C2H5OH) is a soluble, covalent compound. During the experiment, I observed no change in the solution. It was clear. Vegetable oil (C66H100O6) is insoluble in water. It is covalently bonded and forms bubbles of oil on the bottom, sides, and top of water. It does not like to mix with water. Glycerol (C3H8O3) is a covalent compound that is insoluble in water. When mixed with water, small floating white particles remained.
Part 3 Observations:
Part 4 Observations:
Part 5 Observations:
Discussion: Water is known as the universal solvent and is vitally important to the body. Water transports the many water-soluble substances throughout the body, but the substances that are insoluble must be transported in other ways. The type of intermolecular forces that exist within the solute determine whether the substance is soluble or not. The three types of bond in the experiment were polar covalent bonds, non-polar covalent bonds, and hydrogen bonds. Water is a polar covalent substance, and vegetable oil is non-polar. Oils do not adhere easily to other substances due to their non-polarity. Vegetable is also less dense than water, that is why it will float on top of water. Barium compounds are toxic to humans, but patients can take barium sulfate suspensions before upper and lower gastrointestinal tract x-rays because it is insoluble and will be excreted. Regarding oral medical treatments, a drug that is dissolved in syrup will be absorbed more rapidly than a drug in tablet form because it does not have to deaggregate like the solid tablet into chunks, and broken down even smaller. In syrup form, it is already down to the molecular level and is readily absorbable. In part IV of the experiment, after the initial reading, the solution was unsaturated. After heating sodium thiosulfate in water, it dissolved and became a saturated solution. The solution was still saturated after cooling to room temperature, but because supersaturated after adding another seed crystal. It was unstable. In part V, the water must be added to the sodium hydrogen carbonate and citric acid after the two were mixed was because the two compounds had to be mixed together to create an even solution before adding water. C6H8O7 + 3NaHCO3 ---> C6H5O7Na3 + 3CO2 + 3H2O
Error: In this experiment, one error of measurement was the way each compound was measured for the tests. Each measurement was an estimate by using the tip of a spatula but no exact amount was stated, and therefore made it unsure whether or not the right amount of a substance was being used. Conclusion: In this experiment, water was the main solvent. Many chemicals were mixed into water to determine their solubility. It was found in part III of the experiment, that the sucrose solutions that were stirred greatly affected the time it took to dissolve. The stirred solutions dissolved in less than 6 minutes. What also helped to dissolve the sucrose was heat, and if the sucrose was finely ground, making it easier to dissolve in water. Supersaturation was demonstrated when the sodium thiosulfate solution was heated, cooled to room temperature, then added another seed crystal. It was observed in part II of the experiment what kinds of solutions are soluble in water. Sodium sulfate, barium sulfate, naphthalene, vegetable oil, and glycerol were all insoluble in water. Sucrose, urea, and ethanol were soluble in water. Reference: Chem. 1280 Laboratory Manual: Aqueous Solutions. 2010. Cengage Learning. Mason, OH.
Aqueous Solutions
Amal Abdoney CHEM 1290-002 09-06-2011