1. Chapter 15 Solutions

2. Obj. 1-2…Vocabulary solution : solution : homogenous mixture ~ smallest particles ~ no Tyndall effect ~ won’t settle out solutesolvent ~ composed of solute and solvent gets dissolved does the dissolving ** always more solvent than solute! ** name the solute/solvent in the following solutions… salt water solute solvent saltwater atmosphere N2N2N2N2 other gases brass (Zn and Cu) CuZn

3. Obj. 1-2 cont… solubility : solubility : the amount of solute that will dissolve in a solvent at a given temperature. miscible : miscible : liquids that are capable of dissolving each other. (alcohol and water) immiscible : immiscible : liquids that are insoluble in each other… they ‘don’t mix’. (oil and water) solvation : solvation : the process that occurs as an ionic solute dissolves. dissociates ~ solute breaks apart ( dissociates ) into cation (+) ~ solvent particles surround individual ions ~ WILL NOT occur if ionic bonds are stronger than their attraction to the solvent. and anion(-).

4. Obj. 1-2 cont… hydration : hydration : solvation in which water is the solvent.

5. Obj. 3…Solvation Rules in order for solvation to occur, a solute must be broken apart and surrounded by solvent particles. use the rule ‘like dissolves like’ to predict whether solvation will occur. ~ polar (ionic) solvents dissolve polar solutes ~ non-polar (covalent) solvents dissolve non-polar solutes starts w/ metal (cation) starts w/ metal (cation) starts w/ non-metal starts w/ non-metal will solvation occur in the following examples?!?! ~ NaCl and H 2 O yes yes ~ KCl and C 6 H 6 no no ~ P 2 O 5 and H 2 O no no ~ CCl 4 and C 6 H 6 yes yes

6. Obj. 4-5…Solvation of Solids and Gases In general, chemical rxns. are more likely to occur if they are exothermic and increasing in entropy. exothermic an exothermic reaction releases thermal energy to the environment. endothermic an endothermic reaction absorbs thermal energy from the environment. entropy(ΔS) entropy (ΔS) is a measure of disorder of a system. All natural processes tend to increase in entropy. ~ high entropy = more disorder Ex… solid gas low ΔS high ΔS Rxns. w/ more products than reactants! high ΔS

7. Obj. 4-5 cont… the solvation of solids is an endothermic process Must contain huge amounts of entropy in order to occur spontaneously. dissociation (seperation into ions) requires energy! ~ one salt crystal dissociates into millions of ions! The problem with solids… The solution…

8. Obj. 4-5 cont… the solvation of a gas requires a decrease in entropy Reactions must be largely exothermic in order to occur spontaneously. (liquids have less entropy than gases) The problem with gases… The solution…

9. Obj. 6…How Pressure & Temperature Affect Solvation IN GENERAL …solubility rate of solid in a liquid: temp ↑ causes solubility ↑ (sugar is more soluble in hot tea than iced tea) IN GENERAL …solubility rate of a gas in a liquid: warm soft drinks quickly go ‘flat’ CO 2 forced into solution in an unopened soda – what happens when it is opened? temp ↑ causes solubility ↓ pressure ↑ causes solubility ↑

10. Obj. 7…Factors Affecting Solubility Important factors affecting solubility rates… ~ particle size/surface area (smaller = more soluble) ~ agitation/stirring (more agitation = more soluble) ~ temperature (depends on solute) solids like hot gases like cold

11. Obj. 10…Dilute vs. Concentrated concentrated solutions concentrated solutions contain a high amount of solute. diluted solutions diluted solutions contain a low amount of solute. ~ ‘strong’ ~ ‘weak’ These terms are not very helpful when describing solution concentration b/c they are completely relative. 1 gram of solute compared to 10 grams = dilute 1 gram of solute compared to 0.1 grams = concentrated

12. Obj. 11…Types of Solutions unsaturated solutions unsaturated solutions contain a less solute than they are capable of dissolving at a given T and P. ~ can hold more…not full yet! saturated solutions saturated solutions contain the max. amount of solute that they are capable of dissolving at a given T and P. ~ equilibrium exists b/n dissolved and undissolved solute. ~ completely full, can’t hold any more! supersaturated solutions supersaturated solutions contain more solute (dissolved) than it is supposed to hold at a given T and P. ~ must heat solution up to allow more solute to dissolve ~ then let it cool down very slowly, undisturbed.

13. Obj. 11 cont… a solubility curve shows saturated solutions of given substances at given temps. ~ any coordinate below this curve = unsaturated ~ any coordinate above this curve = supersaturated

14. Obj. 11 cont… Which substance is most soluble at 40°C? How many grams of NH 4 Cl will dissolve at 50°C? What two substances have the same solubility at 24°C? If you place 70 grams of KBr into 100g of water at 60°C, what type of solution have you made? How many grams of NaNO 3 will dissolve in 300.0g of water at 10.0°C? NaNO 3 ~ 50 grams KNO 3 and Yb 2 (SO 4 ) 3 unsaturated ~ 240 grams (80 x 3)

15. Obj. 8…Precipitates precipitate : precipitate : insoluble an insoluble solid that will separate from a solution during a reaction (double displacement). ~ using solubility rules, we can predict precipitates. CompoundSolubilityExceptions Salts of group 1A and ammonia (NH 3 ) Soluble (aq)Some lithium compounds Ethanoates, nitrates, chlorates, and perchlorates Soluble (aq)Few Exceptions Sulfates (SO 4 )Soluble (aq) Compounds of Pb, Ag, Hg, Ba, Sr, and Ca Chlorides, Bromides, and Iodides Soluble (aq) Compounds of Ag and some of Hg and Pb Sulfides and HydroxidesInsoluble (s) Group 1A compounds. Compounds of Ba, Sr, and Ca (slightly) Carbonates, Phosphates, and Sulfites Insoluble (s) Group 1A and ammonia (NH 3 ) compounds

16. Obj. 8 cont… Predict the precipitate… CompoundSolubilityExceptions Salts of group 1A and ammonia (NH 3 )Soluble (aq)Some lithium compounds Ethanoates, nitrates, chlorates, and perchlorates Soluble (aq)Few Exceptions Sulfates (SO 4 )Soluble (aq) Compounds of Pb, Ag, Hg, Ba, Sr, and Ca Chlorides, Bromides, and IodidesSoluble (aq) Compounds of Ag and some of Hg and Pb Sulfides and HydroxidesInsoluble (s) Group 1A compounds. Compounds of Ba, Sr, and Ca (slightly) Carbonates, Phosphates, and SulfitesInsoluble (s) Group 1A and ammonia (NH 3 ) compounds LiI (aq) + AgNO 3 (aq) LiNO 3 LiNO 3 + AgI AgI (aq) (s) *precipitate* 6NaOH (aq) + Cr 2 (SO 4 ) 3 (aq) 3Na 2 SO 4 3Na 2 SO 4 + 2Cr(OH) 3 2Cr(OH) 3 (aq)(s) *precipitate* +1 +1 +1 +3 -2

17. Obj. 9…Net Ionic Equations net ionic equation a net ionic equation shows the chemical change in a ~ all soluble (aq) compounds are separated into ions. ~ insoluble (s) compounds are written as compounds. To write… ~ write the complete ionic equation.  separate (aq) compounds.  leave (s) compounds intact. solution (formation of precipitate). ~ cross out any spectator ions …  ions that appear on both sides of equation.

18. Obj. 9 cont… Ex… Li +1 + LiI (aq) + AgNO 3 (aq) LiNO 3 (aq) + I -1 +Ag +1 + NO 3 -1 Li +1 +NO 3 -1 + write complete ionic equation… AgI (s) cross out spectator ions… what is left is the net ionic equation ! I -1 +Ag +1 AgI (s) Ex… 6NaOH (aq) + Cr 2 (SO 4 ) 3 (aq) 3Na 2 SO 4 (aq) + 2Cr(OH) 3 (s) 6Na +1 +6OH -1 +2Cr +3 + 3SO 4 -2 6Na +1 +3SO 4 -2 + 2Cr(OH) 3 (s) 6OH -1 + 2Cr + 3 2Cr(OH) 3 (s)

19. Obj. 12-13…Solution Calculations we said that ‘dilute’ and ‘concentrated’ are very Molarity Molarity indicates how many moles of solute are ~ molarity = general terms for solution concentration. dissolved in one liter of solution. moles Liters ~ units = M Ex… What is the molarity of a salt water solution containing 9.0 moles of salt dissolved in 3.0 liters of solution? 9.0 moles 3.0 liters = 3.0 M 3.0 M

20. Obj. 12-13 cont… What is the molarity of 174 grams of NaCl dissolved in Ex… ~ molarity = moles Liters 23 35 174 grams 500.0 mL 58 grams NaCl 1 mole 1000 mL 1 liter = 6.00 M 6.00 M 500.0 mL of solution?

21. Obj. 12-13 cont… Molality Molality indicates how many moles of solute are dissolved in one kilogram of solvent. ~ molality = moles Kg ~ units = m Ex… What is the molality of 199 grams of NiBr 2 in 500.0 grams of water? 199 grams NiBr 2 500.0 grams 219 grams NiBr 2 1 mole 1000 grams 1 Kg = 1.82 m 1.82 m 59 160

22. Other types of solution concentration include… Obj. 12-13 cont… % mass ~ % mass = part whole = mass of solute or solvent mass of solution 100 x Ex… What is the % by mass of 62.0 grams of KCl dissolved in 475 grams of water ? solvent part (solute) % mass = part whole % mass = 62.0 537 = 11.5% 11.5% ** whole = solution… solute + solvent! 537 62.0 + 475 = 537 grams of solution 100 x

23. Obj. 12-13 cont… Ex… How many grams of KOH are required to prepare 450.0 grams of a 30.0% solution? whole (solution) % part (solute) % mass = part whole x x part = % x whole KOH = 0.300 x 450.0 = 135 g 135 g pph ~ pph = parts per hundred ppt ~ ppt = parts per thousand ppm ~ ppm = parts per million

24. Dilution calculations… ~ a dilution = a solution is made less concentrated M 1 V 1 = M 2 V 2 M 1 V 1 = M 2 V 2 Obj. 12-13 cont… (weaker) by adding more solvent.  changes concentration (molarity).  changes volume of solution. initial molarity initial volume final molarity final volume

25. Ex… How many liters of a 12M solution are needed to create M 1 V 1 = M 2 V 2 Obj. 12-13 cont… 2.0 liters of a 4.0M solution? M 1 V 1 V 2 M 2 12 X 2.0 (4.0) = 0.67 liters 0.67 liters 12 X = 8.0 12 X= Ex… What is the molarity of 1.5 liters of solution made from 600.0 mL of 10.0M NaOH? V 1 M 1 V 2 M 2 1.5 X 0.6 (10.0) = 1.5 X = 6.0 1.5 4.0M 4.0M X=

26. Obj. 12-13 cont… Some dilution problems may contain % concentrations instead of molarity… ~ you do NOT have to put % in decimal form…just be consistent! Ex… How many grams of a 25.0% solution of a KCl are needed to prepare 85.0 grams of a 40.0% solution? % 1 mass 1 = % 2 mass 2 mass 1 % 1 mass 2 % 2 25 X 85 (40) = 136 grams 136 grams 25 X = 3400 25 X=

27. Obj. 14…Colligative Properties Colligative properites Colligative properites are properties of solutions that are affected only by the # of particles in the solution. NOT affected by the type of particle!!! Ex… ~ vapor pressure (VP) ~ freezing point (FP) ~ boiling point (BP)

28. Obj. 15…Effect of Solutes on Vapor Pressure Vapor pressure (VP) Vapor pressure (VP) is the P exerted at the surface of a liquid by particles trying to escape the liquid.

29. Obj. 15 cont… adding a nonvolatile solute to a solvent will cause the VP of ~ solute particles replace some solvent particles at the surface of the solution. the solvent to decrease. ~ less solvent particles on surface = less evaporation = lower VP!

30. Obj. 16 and 18…How Solutes Affect BP and FP Boiling pt. (BP) is temp. at which the VP of the liquid = atmospheric pressure. ~ adding solute lowers VP of solvent ~ must add more KE (heat) to equalize the pressures ** solutes RAISE the BP of solutions! (i.e. we add salt before we boil water) pure watersalt water

31. Obj. 16 and 18 cont… Freezing pt. (FP) is temp. at which liquid turns into a solid. ~ adding solute lowers VP of solvent ~ even more KE (heat) must be lost to lock molecules into ** solutes LOWER the FP of solutions! (i.e. we add salt to icy roads…salt is used in making ice cream ) ~ enough KE is lost (removal of heat) that molecules stop moving around and lock into place. place.

32. Obj. 16 and 18 cont… Ionic solutes lower the VP of solvents more than molecular solutes! ~ ionic solutes dissociate (break up into ions) in solvents. ~ molecular solutes stay intact in solvents.  AlCl 3 dissociates into 4 separate ions (1 Al +3 and 3 Cl -1 )  glucose (C 6 H 12 O 6 ) breaks into separate units of C 6 H 12 O 6 … NOT C’s, H’s and O’s! glucose = Al +3 = Cl -1

33. Obj. 17…BP and FP Calculations solutes raise (elevate) the BP of solvents. to calculate how high the BP is elevated… BP elevationΔT BP BP elevation = ΔT BP m (K BP ) + normal BP = m (K BP ) + normal BP molality BP constant *given* *given except…* *water = 100°C* solutes lower (depress) the FP of solvents. to calculate how low the FP is depressed… FP depressionΔT FP FP depression = ΔT FP normal FP- m (K FP ) = normal FP - m (K FP ) molality FP constant *given* *given except…* *water = 0°C* ** ionic solutes affect molality!!! ** CaCl 2 dissociates into 3 ions, so multiply m by 3! ** Round all temps. to the hundredths place! **

34. Obj. 17 cont… Ex… If 52.34 grams of NiBr 2 dissolve in 392.0 grams of water, what is the BP of the resulting solution? BP = m (K BP ) + normal BP BP = m (K BP ) + normal BP 52.34 g NiBr 2 392.0 g water 219 g NiBr 2 1 mole 1000 g 1 Kg = 0.6097 m x 3 = x 3 = 1.829 m (ions) BP = 1.829 (0.512)+ 100°C = 100.94°C 100.94°C 0.936

35. Obj. 17 cont… Ex… If 95.67 grams of CCl 4 dissolve in 981.0 grams of benzene, what is the FP of the resulting solution? (FP of Benzene = 5.53°C) FP = normal FP- m (K FP ) FP = normal FP - m (K FP ) 95.67 g CCl 4 981 g benzene 152 g CCl 4 1 mole 1000 g 1 Kg = 0.6416 m FP = 5.53°C (5.12) =- 0.6416 2.25°C 2.25°C ** molecular, so don’t multiply by anything! 3.285