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Solubility and concentration of mixtures


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Solubility and concentration of mixtures

  2. 2. What is themaximum amountof salt that willcompletely dissolvein a cup of water?
  3. 3. Procedure:1. Put 20 mL of water in a small clear transparent bottle. Add ½ teaspoon of salt and stir until all the salt dissolves.2. To the salt solution in step #1, add ½ teaspoon salt, a small portion at a time and stir the solution to dissolve the salt. At this
  4. 4. 3. Add ½ teaspoon of salt to the salt solution in step #2 and stir the solution. At this point, you have added one and ½ teaspoons of salt.4. Continue adding ½ teaspoon salt to the same cup until the added salt no longer
  5. 5. Q1. How many teaspoons of sugar did you add to 1 cup of water until the sugar no longer dissolves? __________NOTE: In this step, you willobserve that there is alreadyexcess sugar which did notdissolve.Q2. What is the maximum
  6. 6.  In this activity, you have observed that there is a maximum amount of solute that can dissolve in a given amount of solvent at a certain temperature. What do you think is it called? -SOLUBILITY (of the solute)
  7. 7.  The solution that contains the maximum amount of solute dissolved by a given amount of solvent is called a-saturated solution. If you add more solute to the solvent, it will no longer dissolve. The solution has reached its saturation point. The presence of an excess solid which can no longer dissolve is an
  8. 8.  Is there any containerwhere all solidsdissolved? Whichcontainer is this?
  9. 9. A solution is unsaturatedwhen it contains lesssolute than the maximumamount it can dissolve at agiven temperature.
  10. 10.  A more measurable way to find out the solubility of a solute is to determine the maximum amount that can be dissolved in 100 g of solvent at a specific temperature. There are available data from chemistry books that give the solubility of common solutes at particular temperatures. Figure 2 shows the solubility of table salt at
  11. 11. Concentration of SolutionsThe concentrationdescribes the relativeamounts of soluteand solvent in agiven volume of
  12. 12. Observe thedemonstration.
  13. 13. Describe the concentrationsof solutions qualitatively (bysimply observing theirappearance) andquantitatively (by comparingthe number of drops pervolume of water).
  14. 14. From Part 1 of the demonstration, you were able to describe the solutions as having quantitative concentrations of 1 drop/50 mL and 10 drops/50 mL. Qualitatively, you were able to distinguish the bottle with 10 drops/50 mL more concentrated (darker) than the bottle with 1 drop/50 mL.
  15. 15. When there is a large amount of dissolved solute for a certain volume of solvent, the solution is-concentrated.A solution that has a small amount of dissolved solute in comparison to the amount of
  16. 16.  Now that you have distinguished dilute from concentrated solutions qualitatively and quantitatively from your teacher’s demonstration, you can express concentration in other ways such as: (1) percent by volume, which is the amount of solute in a given volume of solution expressed as grams solute per 100 millliter of solution (g/100 mL), and (2) percent by mass, which is the amount of solute in a given mass of solvent expressed
  17. 17.  Labels of products sold often show the concentrations of solutes expressed as percent (%) by volume or mass. The alcohol used as a disinfectant is a solution of 70% ethyl or isopropyl alcohol, meaning 70 mL alcohol. There are also solutions sold as 40% ethyl or isopropyl alcohol. Vinegar is often labeled as “5% acidity,” which means that it contains 5 grams of acetic acid in 100 g of vinegar. The common antiseptic, agua oxinada is a
  18. 18.  The concentration of solid solutions, like gold jewelry, is expressed as karat. Pure gold is referred to as 24 karats. Jewelry that is said to be 18 karats contains 18 grams of gold for every 24 grams of the material, 6 grams consist of the other metal like copper or silver. This material has a concentration of 75% gold, that is, [18/24(100)]. A 14 karat (14K) gold contains 14 grams gold and 10 grams of another metal, making it 58.3% gold.
  19. 19. The following sample problems show you that there is a way to know the exact ratio of solute to solvent, which specifies the concentration of a solution. Sample problem 1How many mL of ethyl alcohol are present in a 50 mL bottle of rubbing alcohol?
  20. 20. Calculation for sample problem 1 Since rubbing alcohol contains 70% ethyl alcohol, it means that 100 mL of rubbing alcohol contains 70 mL ethyl alcohol. So, the following calculations show that in 50 mL of rubbing alcohol, there is 35 mL ethyl alcohol. The water content is most likely more. There is no easy way to determine but it would be incorrect
  21. 21. Sample problem 2A one peso coin has a mass of 5.5 grams. How many grams of copper are in a one peso coin containing 75% copper by mass?
  22. 22.  Calculation for sample problem 2 75% by mass means 75 grams of copper in 100 grams of one peso coin. So, a 5.5 grams coin contains, 75 g copper x 5.5 g coin = 4.1 g copper 100 g coin