Solution Chemistry & Properties of Water

Solution Chemistry & Solution Chemistry & Properties of WaterProperties of Water

Mixtures ReviewMixtures Review• HomogeneousHomogeneous

– SolutionsSolutions

• HeterogeneousHeterogeneous– Suspension - is a fluid containing solid Suspension - is a fluid containing solid

particles that are sufficiently large enough to particles that are sufficiently large enough to settle.settle.

– Colloid - is a substance microscopically Colloid - is a substance microscopically dispersed evenly throughout another dispersed evenly throughout another substance.substance.

– Emulsion - is a mixture of two or more Emulsion - is a mixture of two or more immiscible (unblendable) liquids.immiscible (unblendable) liquids.

Characteristics of solutionsCharacteristics of solutions

• Solution – homogeneous mixtureSolution – homogeneous mixture

a) parts of a solutiona) parts of a solution

i) solute – substance being dissolvedi) solute – substance being dissolved

ii) solvent – substance doing ii) solvent – substance doing dissolvingdissolving

both can be either solid, liquid, or gasboth can be either solid, liquid, or gas

SolubilitySolubility

• Soluble – substance can dissolve in a Soluble – substance can dissolve in a solventsolvent

ex: salt in waterex: salt in water

• Insoluble – substance cannot dissolve Insoluble – substance cannot dissolve in a in a solventsolvent

ex: sand in waterex: sand in water

Solvation In Aqueous Solvation In Aqueous SolutionsSolutions• Solvation – process of surrounding Solvation – process of surrounding

solute solute particles with solvent particles with solvent particlesparticles

Why are some substances soluble in a Why are some substances soluble in a solvent and some others are not?solvent and some others are not?

must be compatibility between solute must be compatibility between solute and solventand solvent

““like dissolves like”like dissolves like”

• Defn – rule used to determine if Defn – rule used to determine if substance will dissolve in anothersubstance will dissolve in another

- based on attractive forces - based on attractive forces between between solute and solvent solute and solvent

““like dissolves like”like dissolves like”

• polar solvents – dissolve polar polar solvents – dissolve polar molecular molecular compounds and ionic compounds and ionic compoundscompounds

ex: salt and water, alcohol and ex: salt and water, alcohol and vinegarvinegar

• nonpolar solvents – dissolve nonpolar solvents – dissolve nonpolar nonpolar compounds onlycompounds only

ex: oil and gasolineex: oil and gasoline

Factors Affecting Rate of Factors Affecting Rate of SolvationSolvation

• How can you dissolve something How can you dissolve something faster???faster???

a)a) increase temp of solventincrease temp of solvent

this accelerates particles creating this accelerates particles creating more particle collisionsmore particle collisions

Factors Affecting Rate of Factors Affecting Rate of SolvationSolvation

b)b) agitate the solutionagitate the solution

more particle collisions between more particle collisions between solute and solventsolute and solvent

c)c) Increase surface area of soluteIncrease surface area of solute

breaking into smaller pieces allows breaking into smaller pieces allows more solute to be in contact w/ more solute to be in contact w/ solventsolvent

SolubilitySolubility

• Defn – max amt of solute that can Defn – max amt of solute that can dissolve in a solvent at a specific dissolve in a solvent at a specific temptemp

how much solute can be put into how much solute can be put into solvent?solvent?

Unsaturated SolutionUnsaturated Solution

• Defn – less than max amt of solute Defn – less than max amt of solute dissolveddissolved

if I put sugar into water and all sugar if I put sugar into water and all sugar is dissolved, solution is unsaturatedis dissolved, solution is unsaturated

Saturated SolutionSaturated Solution

• Defn – contains max amt of solute Defn – contains max amt of solute dissolveddissolved

if I put sugar into water and not if I put sugar into water and not dissolves (you can see the sugar), dissolves (you can see the sugar), the solution is saturatedthe solution is saturated

Supersaturated SolutionSupersaturated Solution

• Defn – contains more solute than Defn – contains more solute than saturated solution at the same saturated solution at the same conditionsconditions

a saturated solution made at high temp a saturated solution made at high temp cools slowly. Slow cooling allows cools slowly. Slow cooling allows excess solute to remain dissolved in excess solute to remain dissolved in solution at lower temperaturesolution at lower temperature

very unstablevery unstable

Sum up SolubilitySum up Solubility

SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

concentration

Solubility CurveSolubility CurveSaturated-Saturated-Line Line represents represents max amount max amount solute that solute that will dissolve will dissolve at a given at a given temperaturetemperature

Temperature

Solu

bili

ty(g

solu

te/

10

0 g

H2O

)

Unsaturated(below line)

Supersaturated(above line)

How does temp affect How does temp affect solubility?solubility?

•The higher the temp, higher the solubility

(for most cases)

Solution ConcentrationSolution Concentration

• Concentration – how much solute Concentration – how much solute dissolved in amount of solventdissolved in amount of solvent

what is difference between what is difference between concentrated and diluted?concentrated and diluted?

Concentrated vs. DiluteConcentrated vs. Dilute

ConcentrationConcentration

• 3 different units of concentration3 different units of concentration

a)a) percent by masspercent by mass

b) molarity (M)b) molarity (M)

c) molality (m)c) molality (m)

Colligative Properties of Colligative Properties of SolutionsSolutions

• Solutes affect the physical properties of Solutes affect the physical properties of their solventstheir solvents

• Colligative properties (defn) – properties Colligative properties (defn) – properties that depend only on the number of solute that depend only on the number of solute particles present, not their identityparticles present, not their identity

• Ex: boiling point, freezing pointEx: boiling point, freezing point

ElectrolytesElectrolytes

• Defn – substances that break up Defn – substances that break up (ionize) in water to produce ions; can (ionize) in water to produce ions; can conduct electricityconduct electricity

- consist of acids, bases, ionic - consist of acids, bases, ionic compoundscompounds

Ex: NaCl Ex: NaCl Na Na1+1+ + Cl + Cl1-1-

HH22SOSO44 2 H 2 H++ + SO + SO442-2-

NonelectrolytesNonelectrolytes

• Defn – do not break up (ionize) in Defn – do not break up (ionize) in water, they stay the same; doesn’t water, they stay the same; doesn’t conduct electricityconduct electricity

- usually molecular/covalent - usually molecular/covalent compoundscompounds

Ex:Ex: sugar sugar CC66HH1212OO66 C C66HH1212OO66

ethanolethanol CC22HH55OH OH C C22HH55OHOH

Acids & BasesAcids & Bases

PropertiesProperties

ElectrolytesElectrolytes ElectrolytesElectrolytes

Sour TasteSour Taste Bitter tasteBitter taste

Turn Litmus RedTurn Litmus Red Turn Litmus BlueTurn Litmus Blue

React with Metals to React with Metals to Slippery feelSlippery feel

Form Hydrogen gasForm Hydrogen gas Ex. Ammonia, Ex. Ammonia,

Ex. Vinegar, milk, sodaEx. Vinegar, milk, soda lye, antacids, lye, antacids,

Apples, citrus fruitsApples, citrus fruits baking sodabaking soda

ChemASAP

Strength of Acids & BasesStrength of Acids & Bases•Strong Acid/BaseStrong Acid/Base

– 100% ionized in water, comes apart completely in water100% ionized in water, comes apart completely in water– Strong electrolyte, conducts electricityStrong electrolyte, conducts electricity– Strong Acids: HCl, HNOStrong Acids: HCl, HNO33, H, H22SOSO44

– Strong Bases: NaOH, KOHStrong Bases: NaOH, KOH

Strength of Acids & BasesStrength of Acids & Bases

Weak Acid/BaseWeak Acid/Base• Does not ionize completely, does not

come apart completely in water• Weak electrolyte, does not conduct

electricity well.• Weak Acids: HF, CH3COOH

• Weak Base: NH3

Neutralization ReactionsNeutralization Reactions

Strong acid + Strong base Strong acid + Strong base Salt + Salt + WaterWater

Ex. HClEx. HCl(aq)(aq) + NaOH + NaOH(aq)(aq) NaCl NaCl(aq)(aq)+ + HH22OO

Acids & BasesAcids & Bases

pHpHpHpH

The pH ScaleThe pH Scale

• The pH scale indicates the hydronium The pH scale indicates the hydronium ion concentration, ion concentration, [H[H33OO

++]]

• In other words how many HIn other words how many H33OO+ + ions are ions are

in a solution. If there are a lot we in a solution. If there are a lot we assume it is an acid, if there are very assume it is an acid, if there are very few it is a base.few it is a base.

The pH ScaleThe pH Scale

0

7INCREASING

ACIDITYNEUTRAL INCREASING

BASICITY

14

The pH ScaleThe pH Scale

pH of Common SubstancespH of Common SubstancespH of Common SubstancespH of Common Substances

Acid/Base IndicatorsAcid/Base Indicators

• An acid-base indicator is a weak acid An acid-base indicator is a weak acid or a weak base. or a weak base.

• An Indicator changes color over a An Indicator changes color over a range of hydrogen ion concentrations. range of hydrogen ion concentrations. This range is expressed as a pH range. This range is expressed as a pH range.

• Some common indicators are: litmus Some common indicators are: litmus paper, cabbage juice, phenolphthalein paper, cabbage juice, phenolphthalein bromthymol blue etc. bromthymol blue etc.

Acid/Base Indicators -Litmus Acid/Base Indicators -Litmus Paper Paper

• Litmus paper is paper that has been Litmus paper is paper that has been treated with a specific indicator treated with a specific indicator

• Litmus paper turns red in acidic Litmus paper turns red in acidic conditions (pH < 7) conditions (pH < 7)

• Litmus paper turns blue under Litmus paper turns blue under alkaline conditions (pH > 7). alkaline conditions (pH > 7).

Properties of WaterProperties of Water

Water is PolarWater is Polar Water is polar because Water is polar because

oxygen is a “bully” oxygen is a “bully” and does not share and does not share the electronsthe electrons..

Oxygen is negative Oxygen is negative with more electrons with more electrons and Hydrogen is and Hydrogen is positive with less positive with less electrons.electrons.

CohesionCohesion

• Cohesion is the Cohesion is the attraction of the attraction of the same type of same type of molecules to each molecules to each other. other.

• Water molecules Water molecules stick together and stick together and “hold hands” with “hold hands” with hydrogen bondshydrogen bonds

Water is the Universal Water is the Universal SolventSolvent

Water is polar and Water is polar and can dissolve both can dissolve both salts, sugars, and salts, sugars, and other molecules.other molecules.

AdhesionAdhesion

• Adhesion is the Adhesion is the attraction of attraction of molecules between molecules between two differenttwo different substances. substances.

• Example: The Example: The attraction of water attraction of water molecules to a molecules to a glass. glass.

AdhesionAdhesion

Adhesion causes the Adhesion causes the water molecules to water molecules to stick to the sides of stick to the sides of the graduated the graduated cylinder creating a cylinder creating a meniscusmeniscus. .

Adhesion causes Adhesion causes water to rise in a water to rise in a straw. straw.

Water: Acids and BasesWater: Acids and Bases

Property of water – a Property of water – a water molecule can water molecule can split to form ions split to form ions and make acids and make acids and bases.and bases.

Acid: pH 0-6.9Acid: pH 0-6.9

H+ ionsH+ ions

Base: pH 7.1-14Base: pH 7.1-14

OHOH- - ionsions