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Solutions

Solutions. Definitions. Solution: homogeneous mixture of 2 or more substances in a single physical state Solute: the substance dissolved in the solution Solvent: the substance the solute is dissolved in. General Properties of Solutions. 1. solute particles in solutions are very small

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Solutions

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  1. Solutions

  2. Definitions • Solution: homogeneous mixture of 2 or more substances in a single physical state • Solute: the substance dissolved in the solution • Solvent: the substance the solute is dissolved in

  3. General Properties of Solutions • 1. solute particles in solutions are very small • 2. solute particles are evenly distributed throughout the solution • 3. particles in a solution will not separate under normal conditions

  4. Types of Solutions • Aqueous solutions: solutions with water as the solvent. • Electrolyte solutions: aqueous solutions of ionic compounds. Ionic compounds dissociate allowing for the solution to conduct an electrical charge • Nonelectrolyte solutions: aqueous solutions of molecular compounds. The solute does not dissociate.

  5. Solution Concentrations • Amount of solute in a given amount of solvent or solution

  6. Mols of solute Liters of Solution M = Molarity (M) • Most common expression of solution concentration

  7. What is the molarity of a solution formed by mixing 38 grams of potassium hydroxide in enough water to make 250 mL of solution?

  8. If I have a 2.5 M sulfuric acid solution, how many liters of solution will be needed to obtain 70 grams of sulfuric acid? How many milliliters?

  9. Moles of solute Kilograms of solvent m = Molality (m)

  10. Chlorine is often added to water in swimming pools and to drinking water to keep the water clear and free of living organisms. What is the molality of a solution made up of 16.1 g of chlorine in 5000 g of water?

  11. Moles of solute or solvent Total moles of solution Mole Fraction = Mole Fraction (X)

  12. What are the mole fractions of the solute and solvent of the solution prepared by dissolving 50 grams of sodium chloride in 200 grams of water?

  13. Saturation • Saturated: solution contains all possible solute under current conditions • Unsaturated: more solute can be dissolved • Supersaturated: solution contains solute past the saturation point for the current conditions

  14. Changing the Concentration of a Solution (Diluting) M1V1 = M2V2

  15. What volume of 18 M sulfuric acid is needed to create 6 Liters of 3.25 M sulfuric acid?

  16. Solution Formation • When ionic compounds dissolve in water, they dissociate NaCl --> Na+ + Cl- • Each component has an attraction to a certain part of the water molecules

  17. Solubility • the amount of solute that will dissolve in a specific solvent under given conditions • Three factors that influence solubility: • Nature of Solute and Solvent • Temperature • Pressure

  18. Factors Affecting Solubility • Nature of Solute and Solvent: • "likes dissolve likes" • polar will dissolve polar • nonpolar will dissolve nonpolar • Ionic compounds are polar, so they will always dissolve in water.

  19. Factors Affecting Solubility • Temperature: • with gas-liquid solutions, solubility decreases as temperature increases • with solid-liquid solutions, solubility increases as temperature increases

  20. Factors Affecting Solubility • Pressure • in a gas-liquid solution, solubility increases as pressure increases

  21. Factors Affecting Dissolving Rate • Surface Area • the amount of area exposed to the solvent • Stirring • Temperature

  22. Colligative Properties of Solutions -depend upon the concentration of solute in the solution.

  23. Vapor Pressure Reductions • Vapor pressure - the gas pressure resulting from vapor molecules over a liquid. • As concentration increases, vapor pressure is reduced.

  24. Boiling Point Elevation • As concentration increases, boiling point increases. • Relates back to vapor pressure. • Boiling point is the temperature where the vapor pressure of a liquid is equal to external pressure on its surface. ΔTb = Kbm Kb=molal boiling point constant m = molality

  25. Boiling Point Elevation • 39 grams of sodium chloride are added to 500 mL of water. What will the boiling point be? • While cooking some noodles, Pete adds salt to the water (3.25 Liters) as he heats it. How many grams of salt did he add if the boiling point of the solution was 101.3˚C?

  26. Freezing Point Depression • Freezing point is the temperature at which the vapor pressure of liquid and solid phases is the same ΔTf = Kfm Kf = molal freezing point constant m = molality

  27. Freezing Point Depression • How many grams of salt would be needed to reduce the freezing point of 2 kg of water to -15˚C?

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