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Solubility

Solubility. Define: miscible, saturated, unsaturated, solubility, supersaturation . Describe factors that effect solubility. Use “solubility rules” to predict the solubility of an ionic compound in water. Interpret and construct solubility curves.

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Solubility

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  1. Solubility Define: miscible, saturated, unsaturated, solubility, supersaturation. Describe factors that effect solubility. Use “solubility rules” to predict the solubility of an ionic compound in water. Interpret and construct solubility curves. Use solubility curves to distinguish among saturated, supersaturated, and unsaturated solutions. Apply the “like dissolves like” rule to real-world situations. Materials: Salt, Alcohol, Water, Test Tubes, Test Tube Rack

  2. Aim: How can we predict the solubility of a solute in a solvent? Essential Questions: • What are the factors that affect solubility? • How do we use “solubility rules” to predict the solubility of an ionic compound in water? Explain. • What does a solubility curve show and how do we use it? Key Words: miscible, saturated, unsaturated, solubility, supersaturation

  3. Do Now Reference Table F was used to identify the precipitate in double-replacement reactions (see notes from previous week). Use the solubility rules in Table F to classify each of the five compounds given below as solubleor insoluble. • NaNO3 _____________________ • BaSO4 _____________________ • (NH4)2S _____________________ • AgI _____________________

  4. NaNO3 _____________________ BaSO4 _____________________ (NH4)2S _____________________ AgI _____________________

  5. Answers • NaNO3 Soluble • BaSO4insoluble • (NH4)2S soluble • AgI insoluble

  6. Salt/Alcohol + Water Demo • Why won’t the salt dissolve after a certain amount has been added? • What do we call this point? • What do we call it before we reach this point? • How can we get a supersaturated solution? • Does the same phenomenon occur between alcohol and water? • What can we call a solution between alcohol and water?

  7. Notes • Solubility • Definitions • Saturated Solution - a solution where the solvent can no longer dissolve more solute at a certain temperature • UnsaturatedSolution - a solution that has not yet reached its saturation point. • Supersaturated Solution – a solution which holds more solute that can be dissolved at a certain temperature

  8. Notes 4. Soluble – a substance that can form fairly concentrated solutions 5. Miscible – a solution that can be mixed in all proportions of solutes to solvent without hitting a saturation point. Most liquid-liquid solutions and all gas-gas solutions are miscible. 6. Insoluble – A substance that can form only very dilute solutions.

  9. How can we define solubility?

  10. Notes • Solubility - the ability and quantity of solute needed to saturate a given amount of solvent. • The unit used to designate this number is grams of solute per 100 grams of solvent. Ex. at 53 C, 85 grams of KNO3 will saturate 100 grams of H2O. Therefore, the solubility of KNO3 at 50 C is reported as: 85 grams KNO3 per 100 grams H2O.

  11. Solubility Curves • Answer the following questions based on the solubility chart on the left • What is the maximum amount in grams of hydrochloric acid that can dissolve in 100 g of water in 80 C? How about in 40 C? • ____________ ____________ • What is the maximum amount in grams of salt that can dissolve in 100 ml of water in 80 C? How about in 40 C? • ____________ ____________

  12. Notes B. Solubility Chart (Reference Table G) Solubility curves show the concentration of a saturated solution at varying temperatures.

  13. Thought Questions Based on the solubility curve in the previous slide, we can see that solubility increases with increasing temperature. • How can you explain 3 curves on the table which show that solubility decreases with increasing temperature? B. What do you predict will happen if I prepare a solution to saturation at a high temperature and then slowly decrease the temperature?

  14. Notes C. The solubility of a gas in water decreases as the temperature increases. Ex: HCl (aq) SO2 (aq)

  15. D. Supersaturated Solution – Usually, when a solution is prepared at a higher temperature and then cooled slowly, the solute is still suspended in the solution in an unstable way. • Ex. Honey – After a period of time, the excess sugar in honey will crystallize at the bottom of the jar. The honey can be restored to its original supersaturated state by heating it and then allowing it to cool slowly

  16. What Are Some Factors that Effect Solubility Hint: Think about why your soda needs to be chilled or coffee needs to be heated.

  17. Notes E. Factors that affect solubility • Temperature • Nature of Solute & Solvent • If the solute is a gas: Atmospheric Pressure

  18. Learning Check Use reference table G to answer the following questions: • A solution containing 95 grams of KNO3 dissolved in 100 grams of water at 55 C is classified as being • saturated b. unsaturated • supersaturated d. ultrasaturated 2) What is the maximum number of grams of NH4Cl that will dissolve in 200 grams of water at 70 C? • 62 b. 124 c. 70 d. 226

  19. Learning Check 3) Approximately how many grams of KClO3 are needed to saturate 100 grams of H2O at 40 C? • 6 b. 14 c. 37 d. 47 4) Which of the following is most soluble at 60 C? a. NH4Cl b. NaNO3c. KNO3d. KI 5) Which saturated solution is the most concentrated at 20 C? a. NaClb. KClO3c. KI d. KNO3

  20. Notes Solubility

  21. Solubility • Definitions • Saturated Solution - a solution where the solvent can no longer dissolve more solute. • UnsaturatedSolution - a solution that has not yet reached is saturation point. • Supersaturated Solution - Occasionally, when a solution is prepared at a higher temperature and then cooled slowly, the solute is still suspended in the solution in an unstable way. • Ex. Honey – After a period of time, the excess sugar in honey will crystallize at the bottom of the jar. The honey can be restored to its original supersaturated state by heating it and then allowing it to cool slowly

  22. Miscible – a solution that can be mixed in all proportions of solutes to solvent without hitting a saturation point. Most liquid-liquid solutions and all gas-gas solutions are miscible. Soluble – a substance that can form fairly concentrated solutions Insoluble – A substance that can form only very dilute solutions, Solubility of Solute-Solvent Pair - the quantity of solute needed to saturate a given amount of solvent. The unit used to designate this number is grams of solute per 100 grams of solvent. Ex. at 53 C, 85 grams of KNO3 will saturate 100 grams of H2O. Therefore, the solubility of KNO3 at 50 C is reported as: 85 grams KNO3 per 100 grams H2O.

  23. B. Factors that affect solubility • Temperature • Nature of Solute & Solvent • If the solute is a gas: Atmospheric Pressure • C. Solubility Chart (Reference Table G) • 1. Solubility curves show the composition of a saturated solution at varying temperatures.

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