Learning Objectives Explain, in terms of composition and properties, why all solutions are...

Learning Objectives• Explain, in terms of composition and properties, why all solutions are

homogeneous mixtures• Label the solute and solvent of a solution• Describe how temperature, pressure, and the nature of the solute and solvent

affect solubility• Predict the solubility of a substance in a polar or nonpolar solvent according to the

general rule for solubility• Determine if a substance is soluble or insoluble in water using the Solubility

Guidelines in Aqueous Solution Reference Table F• Use the Solubility Curves Reference Table G to classify a solution saturated,

unsaturated or supersaturated at a stated temperature• Express the concentration of a solution in molarity, percent concentration by mass

or volume, and parts per million• Perform mathematical calculations to determine the amount of solute and solvent

in a solution of known molarity, percent concentration, or parts per million• Describe the proper procedure for preparing a solution of known molarity• Relate the concentration of dissolved particles to the boiling point and freezing

point of the solution

What do we know about water?

MP= _0oC__ Bond type= _PC__

BP= _100oC_ Molecule Shape_Bent_

FP= __0oC__ Molecular Polarity_P_

Type of IMF __strong Hydrogen Bonding___

Draw a WATER molecule:

Special Characteristics of H2O:

• Capillary Action: Water climbs up a narrow tube• Adhesion: water is attracted to other materials

(meniscus)• Cohesion: water clings to itself

• Surface Tension: strength of H bonding causes water molecules to be attracted inward (bugs can walk on water, rain drops, etc.)

Mixtures• Ratio of components can vary

• Can be separated physically

• Can be homogeneous or heterogeneous

  MIXTURE COMPOUND Components?

Elements and/or compounds 

 2 or more different elements

Combined physically or chemically?

 physically

 chemically

Homogeneous or Heterogeneous?

homogeneous OR heterogeneous

onlyhomogeneous 

 Represented by formula?

Maybe, followed by the subscript (aq)

Always, 2 or more different capital

letters, subscript: s, l, g 

Are properties the same or different than of components?

Components retain their own properties 

Properties are different 

a.How decomposed into components?b. Sample means of separation?

a. physically b. filtration, distillation

a. chemically b. electrolysis

Solution: homogeneous mixture of 2 or more compounds

• Aqueous: solution in which water is the solvent

Characteristics of a solution:

1. Transparent2. Particles will not settle out3. Can NOT be filtered4. Homogeneous 5. Can have color

NaCl(aq)

1. SOLUTE: substance that gets dissolved* Substance present in the smaller amountNaCl

2. SOLVENT: substance that does the dissolving * Substance present in the greater amountwater

Soda Water• A mixture of a GAS (CO2(g)) in a LIQUID

• The solvent is WATER and the solute is CO2(g)

Tincture• Solution in which alcohol is the

solvent

• Used to dissolve NP substances

• Ex: Iodine

Why is a solution a mixture?

1. ratio of solute & solvent can vary

2. Physically combined & separated

How to separate a solution into its components?

Evaporation/Dehydration Distillation

Distillation• Separation of 2

or more LIQUIDS by BP

• Liquid with lower BP boils first, rises then condenses into a collection vessel.

• Liquid with higher BP stays in original vessel

Types of solutions:

• Dilute: soln having a low amount of solute• Concentrated: soln having a high amount

of solute• Saturated: soln having the maximum

grams of solute at a given temperature• Unsaturated: soln that can hold (dissolve)

more grams of solute at a given temperature• Supersaturated: soln having more grams

of solute than it can hold at a given temperature UNSTABLE!!!!

Solution EquilibriumIn a saturated soln, the

rate of dissolving=rate of crystallization

Reference Table F:Solubility Guidelines for

Aqueous Solutions

Use ref. table F to determine if the following are soluble (S) or insoluble (I or

ppt)1. KBr 8. KClO3

1. NaHCO3 9. NH4OH

1. Al(OH)3 10. CaCO3

1. Cu(NO3)2 11. CuS

1. Fe3(PO4)2 12. ZnI2

1. PbSO4 13. Mg(C2H3O2)2

1. K2S 14. PbCrO4

Use ref. table F to determine if the following are soluble (S) or insoluble (I or

ppt)1. KBr 8. KClO3

1. NaHCO3 9. NH4OH

1. Al(OH)3 10. CaCO3

1. Cu(NO3)2 11. CuS

1. Fe3(PO4)2 12. ZnI2

1. PbSO4 13. Mg(C2H3O2)2

1. K2S 14. PbCrO4

Reference Table G: Solubility Curves

Table GSolubility Curves at Standard Pressure

Solving Solubility Problems using Ref. Table G:

1.) Identification of a. solute ( formula and mass(g)) b. temperature(s) c. grams of water (solvent) 2.) Use table G to solve based on 100g H2O a. 1 temp: solve directly b. 2 temp: subtract solubilities at each temp. 3.) If solvent is NOT 100g: set up a proportion solubility from graph = x________ 100g H2O g H2O from problem

How many grams of KCI are required to saturate 100g water at 60oC?

Which mass of KI will supersaturate 100g H2O at 16oC?

130g 140g 150g

At which temperature will 80g KNO3/100g H2O be supersturated?

40oC or 50oC?

Which of the following would result in an unsaturated solution of NaCl at 90oC?

30g 40g 50g

Formation of a precipitate:

• When a saturated solution is cooled, solid precipitate forms as the solubility decreases.

• (the solvent can’t “hold” as much solute so it “falls out of solution”

• Hint: 2 temps are given

How many grams of KCI will precipitate out when a saturated solution in 100g water is cooled from 90oC to 70oC?

Practice: 1. Classify the following as unsaturated, saturated, or supersaturated :

a. 115g NaNO3 at 25oC ____________________________

b. 115g NaNO3 at 50oC ____________________________

c. 60g NH3 at 10oC ____________________________

d. 50g KClO3 at 89oC ____________________________

e. 50g KCl at 89oC ____________________________

2. At what temp. do KClO3 & KCl have the same solubility? ________________________

3. How many grams of KNO3 are required to saturate 100g water at 45oC? __________________

4. At what temp will 100g KNO3 saturate 100g water? ___________________________________

5. At 50oC, 100g water is saturated with KNO3 . How many grams of KNO3 will precipitate out when the solution is cooled to 40oC?

 6. How much KClO3will precipitate out when a saturated solution in 100g water is cooled from 30oC to 3oC?

7. What is the smallest mass of water required to dissolve completely 23g ammonium chloride at 40oC?

8. How many grams of NaCl are required to saturate 500g water at

100oC?

9. If 75g of a substance will saturate 20g water, what is the solubility

of the substance?

A student was able to dissolve 20g of water with 15.2g of a substance at 46oC. Identify the solute.

Solubility Curves pg 19 HMWK:

1. SO2, NH3, HCl gas2. more3. KClO39. KNO3

4. NaCl 10. 21g5. 95oC 11. 10g6. NH4Cl 12. 12g7. 40g8. 200g

Factors that affect solubilityTemperature

1. Heat on dissolving a solid in a liquid:

increases – more dissolves (heat up sugar & water to make it dissolve2. Heat on dissolving a gas in a liquid: decreases

Factors that affect solubility

Pressure

1. pressure on dissolving a solid in a liquid:

no effect

2. Pressure on dissolving a gas in a liquid: increases ( propane tank, can of soda)

Gases have increased solubility under

___________ Temp, __________ Pressure

Factors that affect solubility

Nature of Reactants

1. Determine POLARITY of solute & solvent

2. Solubility rule: “LIKE DISSOLVES LIKE”

Factors that affect solubility

Nature of Reactants

1. Polar & Ionic will dissolve in _polar_ solvents, NOT __NP___solvents

2. Nonpolar solutes will dissolve in _NP__ solvents, NOT in _P____ solvents

Examples of common solvents

POLAR• Water, H2O

• Alcohol, CH3OH & C2H5OH

NONPOLAR• CCl4

• Liquid benzene & toluene

Alcohol• Are slightly polar so they will dissolve

BOTH polar & nonpolar solutes

• BUT NOT IONIC solutes!!!!

LIKE DISSOLVES LIKESubstance polarity substance polarity will they mix? NaCl H2O _________ ______________

Oil H2O _________ ______________

Br2 H2O _________ ______________

KCl Br2 _________ ______________

NH3 CCl4 _________ ______________

NH4Cl CH3OH _________ ______________

NH3 CH3OH _________ ______________

I2 ___________________ CH3OH _________ ______________

What happens when ionic solute is placed into a polar solvent?

What happens when polar solute is placed into a polar solvent?

Dissociation:• Occurs when ionic solids break apart

into ions when placed in a polar solvent (water)

What happens when polar solute is placed in polar solvent?

What happens when polar solute is placed in polar solvent?

Miscible:• 2 liquids that can mix together

– Polar or ionic with polar or ionic

– Nonpolar with nonpolar

Miscible vs. Immiscible

Solubility Rule HMWK:SOLUTES

polar or nonpolar? 

WaterSOLVENTS

CCl4 

Alcohol

1. NaClYES   NO NO 

1. I2NO  YES   YES

1. Ethanol(C2H5OH) YES YES YES

1. Benzene (C6H6) NO YES YES

1. Br2

NO  YES YES

1. KNO3

YES  NO NO

1. Toluene NO YES YES

1. Ca(OH)2

YES  NO NO

9. Use the solubility rule, “like dissolves like” to compare the solubility of solid iodine in liquid benzene (NP):Iodine will dissolve in benzene because both are nonpolar

10.Use the solubility rule, “like dissolves like” to compare the solubility of solid sodium chloride in liquid water and in liquid benzene (NP):NaCl is ionic (EXTREMELY POLAR) and will dissolve in polar water but not in nonpolar benzene.

11.Use the solubility rule, “like dissolves like” to compare the solubility of liquid ethanol in liquid water and in liquid benzene (NP): Ethanol is slightly polar so it will dissolve in both polar water and nonpolar benzene

12.Why does water dissolve so many ionic compounds? Because the polar water molecule has oppositely charged ends which attract the charged ions of ionic compounds.

In the space provided draw a labeled particle diagram to show the dissociation of NaCl ions by water molecules acting on NaCl crystals:

Quantitative expression of concentration:

1. % composition % by mass = grams solute X100 % by volume = mL solute X100

grams solution mL solution

2. Parts Per million (ppm) = grams solute X 1,000,000 grams solution

3. Molarity

Molarity = moles solute “M” = molar or moles/liter Liter solution

% by mass = grams solute% by volume = mL solute grams solution mL solution

Parts Per million (ppm) = grams solute X 1,000,000 grams solution

Steps to calculate MOLARITY:

1.convert grams, if given, to moles: grams = moles X gram

formula mass

2.convert volume to liters, if necessary

3.use formula from table S: Molarity= moles/liters

4.unit for answer is “M”

Calculate the molarity of CuSO4 that contains 80g solute in 500mL of solution.

Calculate the mass of KClO3 needed to make 780mL of a 0.05M solution.

Grams solute Gram Formula Mass Moles Liters Molarity

1 HC2H3O3  1.0  800mL  

2 H3PO4 2.0 2L  

3 50.0gCuSO4*5H2O

   250mL

4 112gKOH

   1.5L

5 100gCaBr2

   750mL

6  500mL 3M NaOH

7  1.5L 6M HCl

8 250mL 2M H2SO4

9 750mL 0.1M KBr

10  2.5L  0.1M Ba(NO3)2

11 X gramsNaOH

 5L 10M NaOH

12 X gramsH2SO4

 750mL 4M H2SO4

13 X gramsKI

1L 0.500M KI

Grams solute Gram Formula Mass Moles Liters Molarity

1 76 g/mol 0.8L 1/.8=1.25M

2 98 g/mol 2/2=1M

3 250g/mol 50/250=0.2 0.250L .2/.250=0.8M

4 56 g/mol 112/56= 2 2/1.5=1.4M

5 200 g/mol 100/200=0.5 0.750L 0.5/0.750=0.67M

6 1.5 moles 0.500L

7 9 moles

8 0.5 moles 0.250L9 0.075 moles 0.750L

10 0.25 moles11 2000g 40 g/mol 50 moles12 294g 98 g/mol 3 moles 0.750L13 83g 166g/mol 0.5 moles

Molarity by Dilution• Acids are usually acquired from chemical

supply houses in a concentrated form. These acids are diluted to the desired concentration by adding water. If all that changes is adding more water to a known molarity of acid, moles acid before dilution (1)= moles of acid after dilution(2). Moles= M x V.

• Dilution formula: M1V1 = M2V2

M1V1 = M2V2

Colligative Properties• Properties that change due to the number of

dissolved particles

Boiling Point ElevationFreezing Point Depression

Boiling Point Elevation• The addition of nonvolatile solute to water

causes the boiling point to raise. (Boils at a temp higher than 100oC)

• This is why you add salt to water when boiling pasta

Freezing Point Depression

• The addition of nonvolatile solute to water causes the freezing point to lower. (freezes at a temp lower than 0oC- stays liquid longer)

• This is why we salt the roads in the winter

Salts that dissociate to produce _more__ moles of ions in

solution cause a _bigger__ effect on BP or FP.

NaCl(s) Na+(aq) + Cl-

(aq)

H2O

CaCl2(s) Ca+2(aq) + 2Cl-(aq)

H2O

Al(NO3)3(s) Al+3(aq) + 3(NO3)-1

(aq)

H2O

Nature of solute on colligative properties:

Ionic solids have a __larger_____ effect on colligative properties than molecular.

NaCl(s) H2O Na+(aq) + Cl-(aq) C6H12O6(s) H2O C6H12O6(aq)

? Which of the following lower the freezing point the most on an icy road?(a) C6H12O6(s) (b) KCl (c) MF2(s) (d) Al(OH)3(s)

? Which of the following raise the boiling point the most when cooking pasta?(a) C6H12O6(s) (b) KCl (c) MF2(s) (d) Al(OH)3(s)

Solubility of a Salt Lab

• Place your group’s data on the data table found on the next slide.

• Calculate the class average and add this column to the data table in your lab.

• Plot, in a third color, the class average on the same set of axes.

Grams KNO3/5gH2O

Grams KNO3/100gH2O

Experimental crystallization temperature

Class Average

1.0 20.0

2.0 40.0

3.0 60.0

4.0 80.0