What are the parts of a solution? What is the solution process:

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2 What are the parts of a solution? o Solute: the thing that gets dissolved (usually solid) o Solvent: the thing that does the dissolving (usually liquid) What is the solution process: Ionic Compound Covalent Compound

3 What makes a solution different than a mixture? o A solution is a mixture that is mixed evenly and never separates (unless YOU separate them) What causes solutions to remain mixed indefinitely? o INTERMOLECULAR FORCES OF ATTRACTION BETWEEN SOLUTE AND SOLVENT PARTICLES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Like dissolves like: polar solvents dissolve polar solutes Non-polar solvents dissolve non-polar solutes

4 What is SOLUBILITY? o The amount of solute that can be dissolved in a certain amount of solvent at a certain temperature. What is the solubility of Pb(NO 3 ) 2 at 50 o C? How many grams of KCl can be dissolved in 100 g of water at 35 o C?

5 Unsaturated, Saturated and Supersaturated o UNSATURATED: o SATURATED: o SUPERSATURATED: (More solute dissolved than should be soluble at that temperature)

6 What does solution concentration mean? o Solute: solvent or solute: solution Dilute vs. Concentrated: What are 2 ways to measure the concentration of a solution? o Molarity (M) o molality (m)

7 Molarity (M) a.k.a. MOLAR CONCENTRATION What is the molarity of a solution containing 42 g of MgCl 2 in 0.9 L of solution? What is the volume a 2.4 M solution that contains 3.3 g of C 2 H 5 OH? How many grams of Cu(NO 3 ) 2 are in 300 ml of a 1.4M solution?

8 molality: (m) What is the molality of a solution that contains 55.6 g of LiOH dissolved in 670 g of water? How many grams of C 12 H 22 O 11 are dissolved in 1239 Kg of water if the molality is 2.5m?

9 What is a colligative property? o A physical property of a solution that can be changed by adding a solute. What are 3 colligative properties? o Vapor pressure o Boiling Point o Freezing Point o Ex: Colligative property PURE water 1.0 M Salt water Vapor pressure 0.05 atm 0.02 atm Boiling point 100 o C o C Freezing point 0 o C o C

10 What does adding a solute do to the boiling point of a solvent? o INCREASES IT o Why? What does adding a solute do to the freezing point of a solvent? o DECREASES IT o Why?

11 How do you calculate the amount that the boiling point will increase if you add a solute to a solvent? o Ex: What is the boiling point of a solution made from 2.0 g of C 3 H 6 O 2 dissolved in 3500 g of water? (K b for water is 0.52 o C/m) How do you calculate the amount that the freezing point will decrease if you add a solute to a solvent? o Ex: What is the of a solution made from 2.0 g of C 3 H 6 O 2 dissolved in 3500 g of water? (K f for water is 1.86 o C)

12 What is a REVERSIBLE REACTION? o A reaction where the reactants react to become products and then the products can react to become reactants. o A REACTION THAT IS NOT FINITE. o There is a forward process. N 2 O 4 2NO 2 o And a reverse process. 2NO 2 N 2 O 4 o Can be written as one equation: N 2 O 4 <--> 2NO 2

13 What is EQULIBRIUM? o When the forward reaction happens at the same rate as the reverse reaction. o The is NO CHANGE IN THE AMOUNT OF PRODUCTS OR THE AMOUNT OF REACTANTS BEING MADE.

14 What is an EQUILIBRIUM EXPRESSION? o A ratio of the concentrations of the products to the reactants o Ex: 2A + 2B <--> A 2 B 2 o Keq = [A 2B 2 ] [A] 2 [B] 2 What is Keq? o A number that is calculated by putting the concentrations of products and reactants found in a system at equilibrium into the equilibrium expression. o Remember: liquids and solids are not included in the Keq What is the ONLY THING that will change Keq of a reaction? o A change in temperature

15 What does Keq tell you about a reaction? o What side of the reaction is favored when the system is at equilibrium (i.e. what there is more of in the reaction system: products or reactants) o If Keq < 1 : more reactants than products; left side favored o If Keq > 1: more products than reactants; right side favored o If Keq = 1: there are an equal number of reactants and products; neither side favored. How do you calculate Keq? o Ex:. PCl 5 (s) + H 2 O (g) 2HCl (g) + POCl 3 (g) At equilibrium [H 2 O]=0.050 M; [HCl]= M; [POCl 3 ]=0.500 M Calculate the value of the equilibrium constant and determine what side of the reaction is favored at equilibrium.

16 What is Q? o The reaction quotient What does Q tell you about a reaction? o Whether or not the reaction is at equilibrium yet o What direction the reaction needs to continue in to get to equilibrium o If Q = Keq the reaction is at equilibrium o If Q < Keq the reaction is NOT at equilibrium and needs to make more products to get to equilibrium o If Q > Keq then reaction is NOT at equilibrium and needs to make more reactants to get to equilibrium.

17 How do you calculate Q? o The same way you calculate Keq. Set up an equilibrium expression, plug in the concentrations and calculate. Compare Q to Keq Ex: 2SO 2 (g) + O 2 (g) 2SO 3 (g) At a certain time for the above system, [SO 2 ]= 0.15M; [O 2 ]= 0.10; and [SO 3 ]=0.15 If the Keq = 5.0 what is Q, has the system reached equilibrium, and if not, what direction does it need to continue in?

18 What is LE CHATELIER S PRINCIPLE? o If a reaction that has reached equilibrium is upset, it will get itself back to equilibrium by speeding either the forward reaction or the reverse reaction. Reaction will replace what is removed or use up what is added. What things upset equilibrium? o Changes in temperature o Changes in amounts or concentrations of reactants or products o Changes in pressure or volume of the reaction flask ONLY AFFECTS GASES!!! (WHY?)

19 Ex: N 2 (g) + 3H 2 (g) <--> 2NH 3 + Heat o What happens to [H 2 ] when N 2 is added? NH 3 is added? NH 3 is removed? The pressure is increased? The volume of the container is increased? The reaction flask is cooled down? The reaction flask is heated up?

20 What does it mean to say that equilibrium lies to one side or another? o Another way to say this is that one side is favored at equilibrium. o It means that there is either more products or more reactants at equilibrium. Ex: Equilibrium lies to the right means that at equilibrium there are more products in the system than reactants. What does it mean to say that equilibirum shifts to one side or another? o It means that after a system is upset and is not at equilibrium anymore, it will fix itself by speeding up either the forward or the reverse reaction to get back to equilibrium. Ex: Equilibrium shifts to the left means that the system is trying to get back to equilibrium by speeding up the reverse reaction to make more reactants.