1. CMH 121 Luca Preziati Chapter 6: Solutions A solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent.

2. CMH 121 Luca Preziati Chapter 6: Characteristics of Solutions 1. The distribution of particles in a solution is uniform. 2. The components of a solution do not separate on standing. 3. A solution cannot be separated into its components by filtration. 4. For any given solvent/solute combination, it is possible to make solutions of many different compositions. 5. Solutions are almost always transparent. Solid solutions are an exception. 6. Solutions can be separated into pure components. The separation is a physical change, not a chemical change. Characteristic of Solutions

3. CMH 121 Luca Preziati Chapter 6: Solubility Solubility: The maximum amount of a solute that dissolves in a given amount of solvent at a given temperature. Solubility is a physical property. Each solid has a different solubility in every liquid: Those with low solubility are said to be insoluble Those with higher solubility are said to be soluble. Some liquids are insoluble in each other, as for example, gasoline in water. Other liquids have limited solubility in each other, as for example, ether in water (6 g/100 g H2O). Still other liquids are completely soluble in each other, as for example, ethanol and water.

4. CMH 121 Luca Preziati Chapter 6: Solubility Saturated solution: A solution in which the solvent contains the maximum amount of a solute that can be dissolved at equilibrium at a given temperature. Unsaturated solution: A solution that contains less than the maximum amount of a solute that can be dissolved at a given temperature. Supersaturated solution: A solution that contains more than the equilibrium amount of a solute that can be dissolved at a given temperature. When this solution is disturbed in any way, the excess solute separates and the equilibrium solubility is restored.

5. CMH 121 Luca Preziati Chapter 6: Factors Effecting Solubility FactorSolid or Liquid in a LiquidGas in a Liquid Nature of Solvent and solute “like dissolves like” Polar is soluble in polar Non-polar in non-polar No effect Temperature Higher T = Higher solubility With a few exceptions Higher T = Lower Solubility With a few exceptions PressureNo effect Higher P = Higher solubility (Henry’s law)

6. CMH 121 Luca Preziati Chapter 6: Percent Concentration % w/v = X 100 Mass of solute (g) Volume of solution (mL) Mass of solute (g) Weight of solution (g) Volume of solute (mL) Volume of solution (mL) % w/w = X 100 % v/v = X 100 %

7. CMH 121 Luca Preziati Chapter 6: Molarity M Problem: You need 1L of a 0.1M solution of NaCl. How many moles of NaCl do you need. How many grams?

8. CMH 121 Luca Preziati Chapter 6: ppm ppm = X 1,000,000 Mass of solute (g) Mass of solution (g) ppm Problem: 1 L of water contains 2mg of Pb. What is the Pb concentration in ppm?

9. CMH 121 Luca Preziati Chapter 6: Dilutions C 1 x V 1 = C 2 x V 2 It works with any Concentration or Volume unit, as long as: C 1 and C 2 have the same unit V 1 and V 2 have the same unit Problem: Suppose we have a bottle of concentrated acetic acid (6.0 M). How would you prepare 200mL of a 3.5 M solution of acetic acid ?

10. CMH 121 Luca Preziati Chapter 6: Water as a solvent Water is a polar molecule; it is capable of dissolving both Ionic compounds Covalent Compounds

11. CMH 121 Luca Preziati Chapter 6: Electrolytes Ions dissolved in water can migrate from one place to another, maintaining their charge as they migrate. The movement of ions constitutes an electric current. Electrolyte: A substance that conducts electric current when dissolved in water. A substance that does not conduct electricity is called a nonelectrolyte. Strong electrolyte: A compound that dissociates completely to ions in an aqueous solution. Weak electrolyte: A compound that only partially dissociates to ions in an aqueous solution.

12. CMH 121 Luca Preziati Chapter 6: Colloids A colloid is a type of mixture in which one substance is dispersed evenly throughout another. A colloidal system consists of two separate phases: a dispersed phase (or internal phase) and a continuous phase (or dispersion medium). A colloidal system may be solid, liquid, or gaseous.

13. CMH 121 Luca Preziati Chapter 6: Colligative Properties Colligative property: Any property of a solution that depends on the number of solute particles, and not on the nature of the particles. Important colligative properties: Freezing-point depression Boiling-point elevation Osmotic pressure Osmolarity = M x i

14. CMH 121 Luca Preziati Chapter 6: Osmosis Isotonic solutions: Solutions with the same osmolarity. Hypotonic solution: a solution with lower osmolarity than blood plasma and red blood cells. Hypertonic solution: a solution with higher osmolarity than red blood cells. Hemolysis: The swelling and bursting of red blood cells because they cannot resist the increase in osmotic pressure when put into a hypotonic solution.