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Solubility and Concentration

Solubility and Concentration. Chemistry Mrs. Coyle. Part I Solubility:. The ability of a solute to dissolve in a solvent. Expressed as g solute/100g H 2 O or g solute/100mL H 2 O . Soluble. • Soluble: a solute that has appreciable solubility. Miscible.

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Solubility and Concentration

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  1. Solubility and Concentration ChemistryMrs. Coyle

  2. Part I Solubility: • The ability of a solute to dissolve in a solvent. • Expressed as g solute/100g H2O or g solute/100mL H2O

  3. Soluble • Soluble: a solute that has appreciable solubility.

  4. Miscible • Substances that dissolve in each other.

  5. Solubility Curves

  6. Precipitate: solute that comes out of solution. •

  7. Types of Solutions • Saturated contains the maximum amount of solute that can be dissolved at the given conditions of T and P. • Unsaturated contains less than the saturated amount of solute. • Supersaturated contains more than the saturated amount of solute by dissolving at higher temp and then cooling.

  8. A supersaturated solution crystallizes after a seed crystal is introduced. http://www.chem.ufl.edu/~itl/2045/change/C12F11.GIF

  9. Rates of Solution • Does every candy you eat take the same time to dissolve?

  10. Factors affecting the rate of dissolving: • Surface Area • Stirring • Temperature (average kinetic energy)

  11. Factors Affecting Solubility • Temperature (affects solid, liquid and gaseous solutes) • Pressure (affects gaseous solutes)

  12. Effect of temperature on solubility of gases. Example:Compare the amount of oxygen dissolved in the waters of the arctic ocean to the amount of oxygen dissolved in warm tropical waters.

  13. Effect of temperature on solubility of solids. • Example: Can you dissolve more sugar in warm water or in cold water?

  14. Solubility Curves

  15. Effect of Pressure on solubility of solids. • Negligible.

  16. Effect of Pressure on solubility of gases. • Henry’s Law: the amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution. • The higher the pressure the higher the solubility of the gas.

  17. Effect of Pressure on solubility of gases. http://www.chem.ufl.edu/~itl/2045/lectures/lec_i.html

  18. Example An unopened bottle of soda has a pressure of 5atm above the liquid, so the concentration of CO2 in the soda is high. Compare that to a pressure of 1 atm above the liquid when the bottle has been opened.

  19. Part II Concentration: • A measure of the amount of solute dissolved in the solution. • Molarity (M) • Molality (m) • Mole Fraction (x) • Percent by Mass (%)

  20. Part II • Concentration

  21. Molarity • A unit of concentration of a solution expressed in moles solute per liter of solution. (Note: 1L = 1 dm3) Moles of Solute Molarity (M) = Liters of Solution

  22. Why Molarity ? http://www.chem.ucla.edu/~gchemlab/volumetric_soln_conc.jpg

  23. Steps involved in the preparation of a standard aqueous solution

  24. Process of making 500 mL of a1.00 M acetic acid solution

  25. Ex. 1 Molarity • What is the molarity of a solution of 8g NaOH in 100mL of solution? • Answer: 2M NaOH

  26. Ex. 2 Molarity • How many grams of NaOH are contained in 2L of a 3M NaOH solution? • Answer: 240g NaOH

  27. Making Dilutions • Moles Solute=M1V1=M2V2 • M molarity • V volume

  28. Ex. 3 Dilutions • How many milliliters of 2.00M MgSO4 solution must be diluted with water to prepare 100.00 mL of 0.400M MgSO4? • Answer: 20.0mL

  29. Percent by Mass % by mass= Mass of solute x 100 % Mass of solution

  30. Percent by Volume % by volume= Volume of solute x 100 % Volume of solution

  31. Part III Molality and Mole Fraction

  32. Molality • Moles of Solute per kilogram of Solvent Molality (m) = moles solute kg solvent

  33. Mole Fraction xsolute = Moles of solute Moles of solution xsolvent = Moles of solvent Moles of solution xsolute + xsolvent= 1

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