Properties ofProperties of

SolutionsSolutions

Changes In StateChanges In State

A Review of MatterA Review of Matter

• Types of matterTypes of matter

• Pure substancesPure substances– Elements – cannot be broken down by chemical Elements – cannot be broken down by chemical meansmeans– Compounds – two or more elements combined in Compounds – two or more elements combined in definite proportions definite proportions

• MixturesMixtures– Homogeneous – evenly mixed, uniform throughoutHomogeneous – evenly mixed, uniform throughout– Heterogeneous – unevenly mixed, varied Heterogeneous – unevenly mixed, varied

composition composition

Increasing Surface Area Increasing Surface Area Increases Dissolution Increases Dissolution

What is a Solution?What is a Solution?

• Homogeneous mixture of substances in Homogeneous mixture of substances in the same state.the same state.

• A solution may be;A solution may be;– A solid A solid solid. Ex. Zn + Cu solid. Ex. Zn + Cu brass (alloy) brass (alloy)– Gas Gas gas. Ex. Air. gas. Ex. Air.– Liquid Liquid liquid. Ex. alcohol + water liquid. Ex. alcohol + water – And, most familiar to you, a substance, usually And, most familiar to you, a substance, usually

a solid, dissolved in water.Ex. NaCl + water.a solid, dissolved in water.Ex. NaCl + water.(sea water)(sea water)

Components of a SolutionsComponents of a Solutions

• A solute is the substance being A solute is the substance being dissolved.dissolved.

• The solvent is the substance that The solvent is the substance that exists in the greater amount, into exists in the greater amount, into which the solute is mixed.which the solute is mixed.

• Ex. In sea water, salt is the solute, Ex. In sea water, salt is the solute, while water is the solvent.while water is the solvent.

• Water’s properties make it a universal Water’s properties make it a universal solvent.solvent.

The Secret To Waters The Secret To Waters Dissolving Power is it’s Dissolving Power is it’s

Polarized NaturePolarized Nature

The polar water molecules surround the solute molecules, forming H-bonds and dipole attractions

Aqueous SolutionsAqueous Solutions

• Solutions of a substance dissolved in Solutions of a substance dissolved in water are termed aqueous and are water are termed aqueous and are written as follows; written as follows;

• NaCl (s) NaCl (s) Na Na++ ( (aqaq) + Cl) + Cl-- ( (aqaq) (where ) (where s = solid, aq = aqueous, and g = gas)s = solid, aq = aqueous, and g = gas)

• The particles of a homogeneous The particles of a homogeneous aqueous solution are very small, will not aqueous solution are very small, will not settle and settle and willwill pass through a filter. pass through a filter.

Mixtures Can Be Mixtures Can Be SeparatedSeparated

Properties of MixturesProperties of Mixtures

• Light will pass directly through a Light will pass directly through a solution.solution.

• The light beam will not be visible in The light beam will not be visible in the body of the solution.the body of the solution.

• Light will be scattered by the larger Light will be scattered by the larger particles of heterogeneous solutions.particles of heterogeneous solutions.

• This is called the This is called the Tyndall EffectTyndall Effect, after , after the scientist who discovered it.the scientist who discovered it.

Colloids and Suspensions Colloids and Suspensions Scatter Light. Solutions Do Scatter Light. Solutions Do

Not.Not.

Summary of Solution Summary of Solution PropertiesProperties• Aqueous solutions are homogeneous Aqueous solutions are homogeneous

mixturesmixtures

• They are clear and do not disperse They are clear and do not disperse light.light.

• Can have color (ex. CuSOCan have color (ex. CuSO44 is blue). is blue).

• Particles will not settle when left Particles will not settle when left standing.standing.

• Particles pass readily through a filter.Particles pass readily through a filter.

SolubilitySolubility

• Ability of a substance to dissolve in Ability of a substance to dissolve in another substance.another substance.

• ““Like dissolves like.”Like dissolves like.”– Polar molecules dissolve in polar substancesPolar molecules dissolve in polar substances– Non-polar (lipids, oils) dissolve in non-polar.Non-polar (lipids, oils) dissolve in non-polar.

• All materials do not dissolve in equal All materials do not dissolve in equal concentrations.concentrations.

SolubilitySolubility• Highly soluble materials are said to be Highly soluble materials are said to be

solublesoluble or miscible. or miscible.• Materials that dissolve very little are said Materials that dissolve very little are said

to be to be insolubleinsoluble or immiscible or immiscible..• A material dissolves because the attraction A material dissolves because the attraction

of the solvent molecules is greater than of the solvent molecules is greater than the attractive force holding the solute the attractive force holding the solute molecules together.molecules together.

• Insoluble materials have a greater affinity Insoluble materials have a greater affinity for their own molecules.for their own molecules.

• These last 2 points is why oil pools These last 2 points is why oil pools together in watertogether in water

Temperature and PressureTemperature and Pressure

• Solubility is relative to changing temperature. Solubility is relative to changing temperature. • Generally, solubility increases with increasing Generally, solubility increases with increasing

temperature.temperature.• Pressure has Pressure has NO EFFECTNO EFFECT on the solubility of on the solubility of

solidssolids and and liquidsliquids (that compressibility thing (that compressibility thing again) ONLY GASES.again) ONLY GASES.

• Gases behave oppositely, they are Gases behave oppositely, they are moremore soluble atsoluble at higher pressurehigher pressure and and lower lower temperaturetemperature (open a warm seltzer bottle and (open a warm seltzer bottle and a cold one at the same time).a cold one at the same time).

Gas Mixtures React Opposite to Gas Mixtures React Opposite to Liquids in Terms of Pressure Liquids in Terms of Pressure

and Temperatureand Temperature

Solubility GraphsSolubility Graphs

• We can look at a graph of solubility We can look at a graph of solubility curves to determine how much curves to determine how much solute can dissolve in a specific solute can dissolve in a specific quantity of solvent.quantity of solvent.

• We need to know;We need to know;– Which soluteWhich solute– What temperatureWhat temperature

• See reference tables F and G.See reference tables F and G.

Table FTable F

• Guidelines for solubility (Table F)Guidelines for solubility (Table F)– Table F is broken down into Ionic Table F is broken down into Ionic

compounds that compounds that areare soluble. Try soluble. Try learning the exceptions, there are fewer learning the exceptions, there are fewer and you’ll know the rules by default.and you’ll know the rules by default.

• There are many Ionic compounds There are many Ionic compounds that are insoluble and many that are insoluble and many exceptions (use the table).exceptions (use the table).

Table GTable G

• Graph of solubility curvesGraph of solubility curves• Broken down into;Broken down into;

– X axis = Temperature in CelsiusX axis = Temperature in Celsius– Y axis = amount of solute per 100g HY axis = amount of solute per 100g H22O.O.

• How to read graphHow to read graph– Trace given info, grams or °C, along Trace given info, grams or °C, along

curve of X and Y axis to find desired curve of X and Y axis to find desired data point for given solute.data point for given solute.

SaturationSaturation• There is an upper limit to how much solute a There is an upper limit to how much solute a

given solvent can hold at a certain given solvent can hold at a certain temperature.temperature.

• When holding the maximum amount of solute When holding the maximum amount of solute the solution is said to be the solution is said to be saturatedsaturated. .

• When a solution is saturated the addition of When a solution is saturated the addition of any more solute will cause a precipitate to any more solute will cause a precipitate to form. form.

• Ex. Have you ever found un-dissolved Ex. Have you ever found un-dissolved substance on the bottom of your coffee or ice substance on the bottom of your coffee or ice tea?tea?

Using Table G Using Table G (solubility (solubility curves) To Predict Solubility of curves) To Predict Solubility of

SubstancesSubstances• Find KNOFind KNO33 (potassium nitrate) in table G. (potassium nitrate) in table G.• At approximately 32°C, 100 grams HAt approximately 32°C, 100 grams H220 can 0 can

hold a maximum of ~50grams of KNOhold a maximum of ~50grams of KNO33. It is . It is saturated at this mass and temperature.saturated at this mass and temperature.

• If the temperature was raised to 50°C, 100g If the temperature was raised to 50°C, 100g of solvent could hold up to ~83 grams of of solvent could hold up to ~83 grams of KNOKNO33. .

• One could add an additional 33 grams of One could add an additional 33 grams of solute to re-saturate the solution. solute to re-saturate the solution.

• If you do not add more solute, the solution If you do not add more solute, the solution would be called would be called unsaturatedunsaturated..

SupersaturationSupersaturation

• This occurs when a solution is heated, This occurs when a solution is heated, saturated and then slowly cooled, creating a saturated and then slowly cooled, creating a new saturation point.new saturation point.

• The solution maintains it’s homogeneous The solution maintains it’s homogeneous appearance.appearance.

• Supersaturated solutions are very unstable.Supersaturated solutions are very unstable.

• Addition of a single crystalline molecule will Addition of a single crystalline molecule will cause the solution to form a precipitate. cause the solution to form a precipitate.

Determining SaturationDetermining Saturation

• Visual inspection: Does the solution Visual inspection: Does the solution contain un-dissolved particles?contain un-dissolved particles?

• Addition of more solid solute:Addition of more solid solute:1.1. Does the solid fall to the bottom?Does the solid fall to the bottom?

• Yes Yes solution is saturated solution is saturated• No No solution is not saturated solution is not saturated

2.2. Does a precipitate form (material comes out Does a precipitate form (material comes out of solution)?of solution)?• Yes Yes solution is supersaturated solution is supersaturated• No No return to (1) return to (1)

Concentration of SolutionsConcentration of Solutions

• Compositions of homogeneous mixtures Compositions of homogeneous mixtures can vary.can vary.

• Two terms are commonly used;Two terms are commonly used;– DiluteDilute– ConcentratedConcentrated

• The above terms are relative, that is, they The above terms are relative, that is, they are not very precise and tell little about are not very precise and tell little about how much solute is present.how much solute is present.

• More precise terms are; More precise terms are; molarity, % mass, molarity, % mass, % volume & ppm % volume & ppm (parts per million).(parts per million).

MolarityMolarity

• Molarity is the number of moles of Molarity is the number of moles of solute per liter of solution.solute per liter of solution.

M = M = # mol solute# mol solute

L solutionL solution

• Molarity can be used as a conversion Molarity can be used as a conversion factor to find Volume and # of mols.factor to find Volume and # of mols.

M M (mol/L)(mol/L) x V x V (L)(L) = # of mol = # of mol

Percent by MassPercent by Mass

• Mass of a certain ingredient divided Mass of a certain ingredient divided by the total mass.by the total mass.

% Mass = % Mass = Mass of partMass of part x 100 x 100

Mass of WholeMass of Whole

Parts Per MillionParts Per Million

• PPM is used when very small PPM is used when very small amounts are present.amounts are present.

• Generally used to report acceptable Generally used to report acceptable levels of toxins, pollutants, poisons or levels of toxins, pollutants, poisons or other trace amounts of substances.other trace amounts of substances.

PPM = PPM = grams of solutegrams of solute x 10 x 1066

grams of solutiongrams of solution

DilutionDilution

• The process of preparing a less The process of preparing a less concentrated solution from a more concentrated solution from a more concentrated one.concentrated one.

MM11 V V11 = M = M22 V V22

• Where MWhere M1 1 and Mand M22 equal the old and new equal the old and new molarities molarities andand……

• VV11 and V and V22 equal the old and new equal the old and new volumes.volumes.