1. SOLUTIONS
2011

2. Components of Solutions

3. Defining Solutions Solute- the substance that is dissolved
Solvent- the substance that does the dissolving
Solution- a homogeneous mixture of a solute dissolved in a solvent
The parts of a solution are indistinguishable from one another
Solutions may exist as homogeneous mixtures of solids, liquids, gases, or combinations of two states

4. Solvation Water molecules are in constant fluid motion
When a solid is added, the water molecules bump into the solid crystals
There is an attraction between the poles of the water molecule and the ions or molecules, that is greater than the attraction between the ions or molecules themselves
The water molecules surround the ions, those ions move away from the crystals, exposing the ions underneath

5. Solution of Ions in Water
Na+
Cl-

6. Solution of Molecules in Water

7. Describing Solutions Qualitatively

8. Saturated Solutions
Solutions that contain the maximum amount of dissolved solute or a given amount of solvent at a specific temperature
Any excess solvent that is added will fall to the bottom of the container
Saturated solutions exist in a dynamic equilibrium- the rate of solvation is equal to the rate of crystallization

9. Unsaturated Solutions
Solutions that contain less dissolved solute for a given temperature
Any excess solvent added will dissolve

10. Supersaturated Solutions
Solutions that contain more dissolved solute than a saturated solution at the same temperature
Supersaturated solutions are formed by heating the solvent to a temperature where it will hold more solute then cooling it slowly
Supersaturated solutions are very unstable- adding a “seed” crystal or disturbing the solution will often cause the solute to “fall out” of solution

12. Describing Solutions Quantitatively

13. Transmittance and Absorbance
Percent Transmittance- the amount of light that is able to pass through a solution
Percent Absorbance- the amount of light absorbed by a solution
Measured using an instrument called a spectrophotometer

14. Molarity
Molarity is a unit of concentration defined as moles of solute per liter of solution
Formula for Molarity: M= mol L

15. Calculating Molarity
A 100.5mL intravenous solution contains 5.10g of glucose (C6H12O6). What is the molarity of this solution?

16. Preparing a Molar Soution
How many grams of CaCl2 would be dissolved in 1.0L of a 0.10M solution of CaCl2?

17. Dilution
Dilution is the process of making a solution less concentrated
Dilution Formula: M1V1=M2V2

18. Dilution
What volume in milliliters of a 2.00M calcium chloride (CaCl2) stock solution would you use to make 0.50L of a 0.300M calcium chloride solution?

19. Molaility
Molality is a unit of concentration defined as moles of solute per kilogram of solvent
Formula for Molality: m= mol kg

20. Calculating Molality
In the lab, a student adds 4.5g of sodium chloride (NaCl) to 100.0g of water. Calculate the molality of a solution.

21. Factors that Affect Solubility

22. Agitation
Agitation is the process of increasing the movement of the solute and solvent molecules
In general as agitation increases, solubility increases

23. Temperature Adding temperature adds kinetic energy to the molecules
In general as temperature increases, solubility increases
Gases are an exception, as the temperature of a liquid-gas solution is increased, the solubility of the gas decreases

24. Surface area
Surface area is the amount of solute that touches the solvent
In general as surface area increase, solubility increases

25. Type of Solvent The general rule is like dissolves like
Polar solvents dissolve ionic compounds and polar covalnet compounds
Nonpolar solvents dissolve only nonpolar solutes

26. Type of Solvent
Solbule- when a substance completely dissolves in another solvent
Insoluble- when a substance is not able to dissolve in a solvent
Miscible- when two liquids are able to form a solution
Imiscible- when two liquids are not able to form a solution

27. Amount of Solute
The amount of solute that is able to dissolve is dependent on all the other factors
Eventually, the solution becomes saturated and no more solute can dissolve
Dynamic Equilibrium- state in which the rate of solvation is equal to the rate of crystalization

28. Reading Solubility Curves

29. Reading Solubility Curves
Each line represents a solution that is saturated solution
Saturated solutions exist in a dynamic equilibrium where solvation and crystallization are occurring at the same rate
Any point above the line where all the solute is dissolved at a certain temperature represents a supersaturated solution
Any point below the line where all the solute is dissolved at a certain temperature represents an unsaturated solution
Solutes whose curves move upward with increased temperature are typically solids because the solubility of solids generally increases with temperature
Solutes whose curves move downward are typically gases because the solubility of gases generally decreases with increasing temperature

30. Electrolytes

31. Electrolytes
Electrolytes are ionic compounds that dissociate in water to form solutions that conduct electrical current
Dissociation is the process of an ionic compound breaking apart into ions
Dissociation of NaCl:

32. Colligative Properties

33. Colligative Properties
Colligative properties are properties of solutiosn that are affected by the number of particles but not the identity of the solute

34. Boiling Point Elevation: A Colligative Property
Boiling point elevation is the temperature difference between a solution and pure solvent
The value of the boiling point elevation is directly proportional to molality, meaning the greater the number of solute particles, the greater the elevation

35. Formula for Boiling Point Elevation:
Kb= molal boiling point elevation constant
The boiling point of pure water= 100°C
Kb for water= °C/m
m-= molality (mole solute/kg of solution)

36. Freezing Point Depression: A Colligative Property
Freezing point depression is the difference in temperature between a solution and a pure solvent
The value of freezing point depression is directly proportional to molality, meaning the greater the number of solute particles

37. Formula for Freezing Point Depression:
Kf= molal freezing point depression constant
The freezing point of pure water= 0°C
Kffor water= 1.86°C/m
m= molality

38. Example- Changes in Boiling and Freezing Points
What are the boiling and freezing points of a m aqueous solution of sodium chloride (NaCl)?

39. Reaction Equilibrium and le Chatlier’s Principle

40. Chemical Equilibrium
Many chemical reaction exist in a dynamic equilibrium meaning the reactions are reversible and products and reactants are made at the same rate

41. Le Chatlier’s Principle:
Le Chatlier’s Principle: If stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress
In general …
We say a reaction shifts to the right when it is moving from reactants to products
We say a reaction shifts to the left when it is moving from products to reactants

42. Changes in Concentration of Reactants and Products
Adding reactants: shits equilibrium right
Adding products: shifts equilibrium left
Removing reactants: shifts equilibrium left
Removing products: shifts equilibrium right

43. Changes in Pressure and Volume
When pressure of a gas is increased, volume is decreased
When pressure of a gas is decreased, volume is increased

44. Increasing pressure of a container in which two or more gases are reacting
Decreases the volume, moving particles closer together
Increases collision of particles
Increase reaction rate, shifting equilibrium right

45. Decreasing the pressure of a container in which two or more gases are reacting
Increases the volume
Particles move apart, decreasing collisions
Decreases reaction rate, shifting equilibrium left

46. Changes in Temperature

47. Exothermic Reactions Reactions that release energy in the form of heat
Represented by the symbol ΔH° which for an exothermic reaction will have a negative value (heat is treated as a product)
Increasing the temperature of an exothermic reaction shifts equilibrium left
Decreasing the temperature of an exothermic reaction shifts equilibrium right

48. Endothermic Reaction Reactions that require energy in the form of heat
Represented by the symbol ΔH° , which for an endothermic reaction will have a positive value (heat is treated as a reactant)
Increase the temperature of an endothermic reaction shifts the equilibrium right
Decreasing the temperature of an endothermic reaction shifts equilibrium left

49. Examples:
Use Le Chatlier’s principle to predict how each of these changes would affect the ammonia equilibrium system: N2 + 3H2  2NH3
Removing hydrogen
Adding ammonia
Adding hydrogen

50. Examples:
Predict how this equilibrium would respond to increasing temperature:
CO + Cl2  COCl2 ΔH°= -220kJ