Ch. 8 Solutions, Acids, & Bases I. How Solutions Form Definitions Types of Solutions Dissolving ...

Ch. 8Solutions, Acids, & Bases


I. How Solutions Form Definitions Types of Solutions Dissolving Rate of Dissolving

A. DefinitionsA. Definitions

Solution – Solution – a mixture that has the same a mixture that has the same composition throughout the mixture; a composition throughout the mixture; a homogeneous mixturehomogeneous mixture

Solvent Solvent – what the solute is dissolved in (in greater quantity)

Solute Solute - substance being dissolved (in lesser quantity)

A. DefinitionsA. Definitions

Solute Solute - KMnO4 Solvent Solvent - H2O

Remember the difference between a a mixture and a compound.

o Compounds have the same (fixed) composition throughout.

o Mixtures can have a variable (different) composition throughout.

A. Definitions

Solubility – The maximum amount of solute that can be dissolved in the solvent at a given temperature.

A. Definitions

B. Types of SolutionsB. Types of Solutions

Saturated solutions – maximum amount of solute at a given temperature.

Unsaturated solutions – less than the max. amount of solute at a given temperature.

Supersaturated solutions – more than the max amount of solute at a given temperature; unstable

B. Types of SolutionsB. Types of Solutions

SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

concentration

C. DissolvingC. Dissolving

SolvationSolvation

• occurs at the surface of the solute

• solvent particles surround solute particles (+/- attraction)

• solute particles are pulled into solution

C. DissolvingC. Dissolving

NaCl dissolving in waterNaCl dissolving in water

D. Rate of DissolvingD. Rate of Dissolving

Solids dissolve faster...Solids dissolve faster...

• more stirring

• small particle size(increased surface area)

• high temperature

D. Rate of DissolvingD. Rate of Dissolving

Gases dissolve faster...Gases dissolve faster...

• no shaking or stirring

• high pressure

• low temperature



II. Concentration & Solubility

A. ConcentrationA. Concentration

% by Volume% by Volume• usu. liquid in liquid• EX: 10% juice = 10mL juice + 90mL water

% by Mass% by Mass• usu. solid in liquid• EX: 20% NaCl = 20g NaCl + 80g water


Concentrated solutionConcentrated solution • large amount of solute

Dilute solutionDilute solution • small amount of solute


SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

concentration

B. SolubilityB. Solubility

SolubilitySolubility• maximum grams of solute that will

dissolve in 100 g of solvent at a given temperature

• varies with temperature• based on a saturated solution


Solubility CurveSolubility Curve• shows the

dependence of solubility on temperature


Solids are more soluble at...Solids are more soluble at...• high temperatures.

Gases are more soluble at...Gases are more soluble at...• low temperatures.• high pressures

(Henry’s Law).



III. Particles in Solution “Like Dissolves Like” Electrolytes

A. “Like Dissolves Like”A. “Like Dissolves Like”

NONPOLAR

NONPOLAR

POLAR

POLAR

DetergentsDetergents• polar “head” with long nonpolar “tail”• can dissolve both types

B. ElectrolytesB. Electrolytes

ElectrolyteNon-

Electrolyte

solute exists asions only

- +

salt

- +

sugar

solute exists asmolecules

only

- +

acetic acid

WeakElectrolyte

solute exists asions and

molecules


DissociationDissociation• separation of +/-

ions when an ionic compound dissolves in water


IonizationIonization• breaking apart of

polar covalent molecules into ions when dissolving in water



I. Intro to Acids & Bases Definitions Properties Uses

A. AcidsA. Acids

• Contain at least one hydrogen atom that can be removed when the acid is dissolved in water.

• These form hydronium ions, H3O+.

HCl + H2O H3O+ + Cl–

A. BasesA. Bases

• Form hydroxide ions (OH-) in a water solution.

NH3 + H2O NH4+ + OH-

A. IndicatorsA. Indicators

• An organic substance that changes color in an acid or base.

ExamplesExamples::• litmus - red/blue• phenolphthalein - colorless/pink• goldenrod - yellow/red• red cabbage juice - pink/green

B. PropertiesB. Properties

sour taste

pH less than 7

corrosive

electrolytes

turn litmus red

react with metals to form H2 gas

bitter taste

pH greater than 7

corrosive

electrolytes

turn litmus blue

slippery feel

C. UsesC. Uses

H3PO4 - soft drinks, fertilizer, detergents

H2SO4 - fertilizer, car batteries

HCl - gastric juice

HC2H3O2 - vinegar

C. UsesC. Uses

NaOH - lye, drain and oven cleaner

Mg(OH)2 - laxative, antacid

NH3 - cleaners, fertilizer



II. Strength of Acids & Bases Strength vs. ConcentrationStrong vs. Weak pH

A. Strength vs. ConcentrationA. Strength vs. Concentration

Strong and weak – tells how easy the acid or base dissociates in solution.

Concentration – The amount of acid or base in a solution.

It is possible to have a dilute concentration of a strong acid that would be less harmful than a concentrated weak acid.

A. Strength of Acids & BasesA. Strength of Acids & Bases

The strength of an acid or base depends on how completely a compound separates into ions when dissolved in water.

Ions can carry an electric charge so a strong acid will carry more electricity than weak acid.

B. Strong vs. WeakB. Strong vs. Weak

Strong Acid/BaseStrong Acid/Base• 100% ions in water• strong electrolyte• HCl, HNO3, NaOH, LiOH

Weak Acid/BaseWeak Acid/Base• few ions in water• weak electrolyte• HC2H3O2, NH3

- +

- +

B. Strong AcidsB. Strong Acids

Acids that ionize almost completely in a solution are strong acids.

Ex: HCl, HNO3, and H2SO4

B. Strong BasesB. Strong Bases

Bases that dissociate completely in a solution are strong bases.

Ex: NaOH

C. pH ScaleC. pH Scale

0

7INCREASING

ACIDITY NEUTRALINCREASING

BASICITY

14

pH pH (potential of Hydrogen)(potential of Hydrogen)• a measure of the concentration of H+

ions in a solution • measured with a pH meter or an

indicator with a wide color range (0-14)

C. pH ScaleC. pH Scale

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

Which of the following "molecular" pictures best represents a concentrated solution of the weak acid HA?

ConcepTestConcepTest

A B

Is the following statement TRUE or FALSE?

• A strong acid has a lower pH than a weak acid.

• FALSE - Strong/weak refers to amount of ionization whereas pH refers to concentration of H+.

ConcepTestConcepTest



III. Neutralization Neutralization Reaction

A. Neutralization ReactionA. Neutralization Reaction

Chemical reaction between an acid and a base.

Products are a salt (ionic compound) and water.

ACID + BASE ACID + BASE SALT + WATER SALT + WATER

HCl + NaOH HCl + NaOH NaCl + H NaCl + H22OO

Neutralization does not always mean pH = 7.

=


KOH + HNO3 H2O + KNO3

Acid

Base

Salt

HNO3

KOH

KNO3


Ch. 8 Solutions, Acids, & Bases I. How Solutions Form Definitions Types of Solutions Dissolving ...

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