SOLUTIONSA solution is a homogeneous mixture; particles are evenly distributed throughout the mixture.• Proportions may vary• Uniform ratio throughout the mixtureA liquid solution is clear. The particles are not visible, do not settle, and can not be filtered.

A solution differs from a suspension in that the particles of a suspension are visible, can be filtered, and settle.

A solution differs from a colloid in that the particles of a colloid exhibit Tyndall effect., yet do not settle.

(TYNDALL effect: the scattering of light by particles such as headlights in fog, flashlight through Jello or dilute milk)

A solution will not exhibit the Tyndall effect.

Cherry Kool-aidRed powder: flavor and colorWhite crystals: sugarClear liquid: water

One substance dissolved in another◦Solute: the substance being dissolved◦Solvent: the substance that dissolves

the solute Sugar is the SOLUTE (smaller quantity) Water is the SOLVENT (larger quantity)

Types of SolutionsGas (solvent is gas)

◦ Gas into Gas: air◦ Liquid into Gas: humidity◦ Solid into Gas: air pollution

Liquid (solvent is liquid)◦ Gas into Liquid: pop◦ Liquid into Liquid: vinegar◦ Solid into Liquid: sweet tea

Solid (solvent is solid)◦ Gas into Solid: absorbent charcoal◦ Liquid into Solid: dental fillings◦ Solid into Solid: alloys of metal

The Dissolving ProcessTwo factors affect the dissolving

process: dissolution◦The constant motion of the particles

(There’s that good old kinetic molecular theory again!)

◦The polarity of the solute and solvent (Recall that polarity is when a compound has partial charges because of uneven distribution of charges)

Steps of the Dissolving Process

1. Moving solvent particles cluster around solute molecules or particles at the surface of the solid.

2. Solvent molecules pull solute off of the solid surface and into solution.

3. Moving solvent particles continue to spread solute evenly throughout the solution,

The process repeats itself as fresh layers of the solute are exposed.

1. Solvent particles cluster around solute particles at the surface.

2. Solvent particles pull solute particles away from surface, into solution.

3. Moving solute particles continue to spread solute evenly through solution.

MOLECULAR

1. Solvent particles cluster around solute particles at the surface.

2. Solvent particles pull solute particles away from surface, into solution.

3. Moving solute particles continue to spread solute evenly through solution.

IONIC

IONIC COMPOUNDSWhen an ionic substance dissolves in

water, the forces of the solvent pulling on the ions is stronger than the forces holding the ions together.

The ions separate. This is called DISSOCIATION

Because charged ions are present in an ionic solution, ionic solutions conduct electricity and are called ELECTROLYTES.

EXAMPLE: NaCl

MOLECULAR COMPOUNDSCertain polar substances form

ions when they dissolve in water. This process is called IONIZATION.

Because ions are formed, the solution conducts electricity.

These substance are also ELECTROLYTES.

EXAMPLE: HCl, HC2H3O2

MOLECULAR COMPOUNDSOther polar substances do not

ionize in water.Because ions are not formed, the

solution does not conduct electricity.

These substances that do not ionize in water and do not conduct electricity are called NON-ELECTROLYTES.

EXAMPLE: sugar

ELECTROLYTES: substances that conduct electricity when dissolved in water

Ionic substances that separate into ions (dissociate) or polar molecular substances that form ions (ionization) when dissolved conduct electricity and are called ELECTROLYTES.

ReviewA substance whose water

solutions do not conduct electricity is a non-electrolyte.◦Many covalent compounds

A substance that separates into ions (dissociates) or forms ions (ionizes) in a water solution conducts electricity and is called an electrolyte◦All ionic and some covalent

compounds

COMPOUNDS THAT DISSOLVE IN WATER

ELECTROLYTESDO CONDUCT ELECTRICITY

IONIC COMPOU

NDS DISSOCIATE INTO

IONS

SOME POLAR

MOLECULAR

COMPOUNDS

IONIZE

NON-ELECTROLYTESDO NOT CONDUCT

ELECTRICITY

OTHER POLAR MOLECULAR COMPOUNDS

DISSOLVE WITH NO FORMATION OF IONS

Factors Solid in Liquid

Gas in Liquid

TEMPERATURE Temp > Rate >

Temp > Rate <

AGITATION Agitation > Rate >

Agitation > Rate <

SIZE OF PARTICLES(surface area)

Size < (surface area

>) Rate >

NA

PRESSURE NA Pressure > Rate >

WHY?(KMT)

The solute particles are

less energetic than solvent

The solute particles are

more energetic than

solvent

FACTORS THAT AFFECT THE RATE OF DISSOLUTION

Think BIGRecall the Pop and Mentos experiment!

The pop “explodes” because the dissolved gas rapidly leaves the solution because the

candy gives it surfaces to collect on (nucleation sites).

Particles in SolutionsSolvents with non-polar

molecules dissolve non-polar substances◦Oil, grease, dry cleaning fluid, paint,

turpentineSolvents with polar molecules

dissolve polar substances◦Water dissolves sugar, ionic

compounds

LIKE DISSOLVES LIKE

TermsSoluble: capable of being

dissolved in a particular solventInsoluble: incapable of being

dissolved in a particular solvent

Miscible: liquids that dissolve freely in any proportion

Immiscible: liquids that are not soluble in each other

Detergents and emulsifiersGrease is non-polarWater is polar

DETERGENT has ◦A non-polar end that dissolves the

grease◦A polar end that dissolves in the

water to rinse it away NONPOLAR DETERGENT

POLARGREASE WATER

CRAFTY CHEMISTRYArtists use physical properties to create inspiring beauty!

ART and SCIENCE

SolubilityThere are limits to the amount of

solute that will dissolve in a given amount of solvent at a given temperature

There are some general terms:◦Unsaturated◦Saturated◦Super-saturated

Unsaturateda solution that can dissolve more

of a given solute at a certain temperature◦A crystal of solute added to an

unsaturated solution will dissolve When you add a second spoon of sugar

to your cup of tea, it dissolves. The tea was an unsaturated solution.

Saturateda solution that has dissolved all of the

solute that it can at a certain temperature◦ A crystal of solute added to a saturated

solution will drop to the bottom, un-dissolved. When you add three spoons of sugar to your tea,

some sugar drops to the bottom, undissolved. It is a saturated solution.

DYNAMIC EQUILIBRIUM exists: ◦ changing but balanced.◦ Some solid dissolves, but as some

dissolves, some re-crystallizes

Super-saturatedan unstable solution that contains

more solute than a saturated solution at a certain temperature◦ A crystal of solute added to a super-

saturated solution will cause crystallization. So will any disruption of the unstable solution.

◦ Make a saturated solution at an elevated temperature and cool it slowly. At the lower temperature, the solute will remain dissolved in an unstable situation. If disrupted, the solute crystallizes. Hot-packs and rock candy

SOLUBILITY CURVE

Max g of solute that will dissolve in 100 g of solvent at a given temperature

Solubility + Gas Laws = Safe SCUBAScience of Diving

Concentration: the amount of solute in a given amount of solvent or solutionDilute: a relatively small amount

of solute in a relatively large amount of solvent

Concentrated: a relatively large amount of solute in a relatively small amount of solvent

We can do better!

Percent by volumemL of solute /100 mL of solution

3% hydrogen peroxide3 mL H2O2 / 100 mL soln

70% isopropyl alcohol (what is different)

70 mL alcohol / 100 mL soln

Percent by massg of solute/100 mL of solutionIV saline.9 g NaCl/100 mL solution x

100% = .9%

IV glucose5 g glucose/100 mL soln x 100%

= 5%

PPM and PPBx/1,000,000x/1,000,000,000

MAWC Annual Report to Consumers

Serial dilutions are often used◦1x, 10x, 100x, 1000x, etc.◦ 1 mL “neat” stock to 10 mL total volume =

10x◦ 1 mL 10x to 10 mL total volume = 100x …

Mass per volumeg solute/1000 mL solution

9 g NaCl/1000mL = 9 g NaCl/LNot that useful to chemist…but

MOLES are!9 g NaCl | 1 mol NaCl = .15 mol

NaCl 1 L soln | 58.44 g NaCl L soln

This helps chemists relate solutions to amounts in chemical reactions, and there is a word for this…

MolarityM = mol solute/liter of solution

Chemists use this because it lets us work concentration into stoichiometry problems

SEE EXAMPLE PROBLEMS

Molarity example 1You have 3.50 L of solution that

contains 90.0 g of NaCl. What is the molarity?

M = mol/L

Molarity example 2You have .8 L of a .5 M HCl

solution. How many moles of HCl does this solution contain?

M = mol/L

To produce 40.0 g of silver chromate, you will need 23.4 g of potassium chromate in solution as a reactant. All you have on hand is 5 L of 6.0 M K2CrO4 solution. What volume of this solution is need to give you the 23.4 g K2CrO4 needed for this reaction?

M = mol/L

Molarity example 3

Molarity Practice

1. What is the molarity of a solution composed of 5.85 g of potassium iodide dissolved in enough water to make .125 L of solution?

2. How many moles of H2SO4 are present in .500L of a .150 M H2SO4 solution?

3. What volume of 3.00 M NaCl is needed for a reaction that requires 146.3 g NaCl?

QuikQuizWhat is the molarity of a solution

of 80. g of NaOH dissolved in 1.0 L water?

2 M = 2 moles per liter!

Molalitym = mol solute/kg of solvent

Chemists sometimes use this because volume of liquids changes with temperature. Soon, we will be studying the effect of concentration as temperature changes.

SEE EXAMPLE PROBLEMS

Molality example 1A solution was made by

dissolving 17.1 g sucrose (molar mass 342.34 g/mole) in 125 g water. What is the molal concentration of this solution (the molality)?

m = mol solute/ kg solvent

Molality example 2A solution of I2 in carbon tetrachloride,

CCl4, is used for chemical tests for starch. How much iodine must be added to prepare a .480 m solution of iodine in CCl4 if 100.0 g of CCl4 is used?

m = mol solute/kg solvent

Practice Molality

1. What is the molality of acetone in a solution composed of 225 g of acetone, C3H6O, dissolved in 200. g water?

2. What quantity, in grams, of methanol CH3OH, is required to prepare a .244 m solution in 400. g of water?

Dilutions: a concentrated solution is diluted by adding more solvent to get the desired concentration.

M1V1 = M2V2

Moles before dilution = Moles after

dilution

◦M = molarity = mol/L◦V = volume = L

◦M x V = mol/L x L = # mol of solute

Dilutions: a concentrated solution is diluted by adding more solvent to get the desired concentration.

The # of moles before dilution is equal to the # of moles after dilution. The same # of moles is present in more solvent. The concentration (M, molarity) changes, the volume (V) changes, but not the # of moles of solute (M x V). ◦ Volume units may vary from L, but must be consistent

within problem.

So, M1V1 = M2V2

SEE EXAMPLE PROBLEMS

Dilution exampleI need 100. mL of 1.00 M HCl. I

have a stock solution of 12.0 M HCl. Describe how to make the solution I need.

M1V1 = M2V2

1.00 M (100. mL ) = 12.0 M (x mL)

X = 8.33 mL 12 M HCl diluted to a total volume of 100. mL

Dilution PracticeHow do you prepare 100 mL

of .20 M HCl from a stock solution of 2.0 M HCl?

M1V1 = M2V2

Making solutions1. “Mass” the solid2. Transfer solid to a small

beaker/flask3. Transfer all of solid by rinsing

weighing paper with water4. Swirl in small quantity of water5. Transfer to volumetric flask with

repeated rinses6. Mix in small quantity of water7. Fill carefully to the line8. Cover with parafilm and mix

thoroughly

Making dilutions

1. Measure quantity of stock solution using graduated cylinder or pipet

2. Transfer completely to volumetric flask with repeated rinses

3. Mix in water4. Bring volume to line 5. Cover with parafilm and mix

thoroughly