Intro to Acids and Bases(again!)

Anion(example)

Acid(example)

_______ ide (chloride, Cl-)

________ate (chlorate, ClO3

-) _________ite (chlorite, ClO2

-)

hydro____ic acid (hydrochloric acid, HCl)

_______ic acid (chloric acid, HClO3)

_______ous acid (chlorous acid, HClO2)

Add H+ Add H+Add H+

Naming acids • An acid is loosely defined as a compound

that produces hydrogen ions (H+) when dissolved in water

• Acids are named depending on the anion in the compound

Acid Anion root NameH2SO4 Sulfate Sulfuric acidH3PO4 Phosphate Phosphoric acidHCl Chloride Hydrochloric acidHC2H3O2 Acetate Acetic acidHNO3 Nitrate Nitric acidHClO2 Chlorite Chlorous acidHClO Hypochlorite Hypochlorous

acid

Writing Formulas AcidsAcid Name Formula Anion Name

Acetic acid HC2H3O2 acetate

Carbonic acid H2CO3 carbonate

Hydrochloric acid HCl Chloride

Nitric acid HNO3 Nitrate

Phosphoric acid H3PO4 Phosphate

Sulfuric acid H2SO4 Sulfate

Names and formulas for Bases A base is a compound that produces

hydroxide ions (OH-) when dissolved in water

Bases are named in the same way as other ionic compounds—the name of the cation is followed by the name of the anion

Examples - Sodium hydroxide (NaOH); potassium hydroxide (KOH)

Strengths of Acids and Bases The strength of an acid/base depends on

how well the ions dissociate Influenced by

Polarity (more polar = stronger) Bond strength (Stronger bonds = weaker

acid/bases because they don’t dissociate) Stability of anion (more stable = stronger)

Strong ≠ high concentration Strength measures the degree of

separation Concentration refers to how many particles

are present

Strength of Acids/Bases Strong acids/bases – completely

dissociate, strong electrolytes Examples you should know: HNO3, H2SO4,

HCl, HBr, HI; KOH, NaOH Weak acids/bases – don’t completely

dissociate and are weak electrolytes Generally, organic acids like acetic acid

(vinegar) Not many weak bases; i.e. NH3

Defining Acids and Bases Multiple ways to define acids and bases Arrhenius acids/bases

Acids are hydrogen-containing compounds that yield hydrogen ions (H+) in aqueous solution

Bases yield hydroxide ions (OH-) in aqueous solution

Arrhenius AcidsH+ is also known as a protonAcids can be monoprotic, diprotic, or

triprotic Monoprotic: HNO3 → H+ + NO3

-

Ionization yields one hydrogen ion Diprotic: H2SO4 → 2H+ + SO4

2-

Complete ionization yields 2 hydrogen ions Triprotic: H3PO4 → 3H+ + PO4

3-

Complete ionization yields 3 hydrogen ions

Arrhenius AcidsNot all the hydrogens in an acid may be

released as hydrogen ionsNot all hydrogen-containing compounds

are acids Only hydrogens joined to very electronegative

elements with very polar bonds, are ionizable in water

H

H

H

H+C C O-

O

Ethanoic Acid

Nonionizable HydrogenIonizable Hydrogen

Arrhenius BasesBases formed with group one metals

are very soluble and caustic NaOH → Na+(aq) + OH-(aq) KOH → K+(aq) + OH-(aq)

Bases of group 2 metals are very weak Examples are Ca(OH)2 and Mg(OH)2

Bronsted-Lowry Acids and Bases Arrhenius definition is not very comprehensive

Ammonia (NH3) is a base, but there is no hydroxide (OH-) in the compound to ionize

The Bronsted-Lowry theory defines an acid as a hydrogen-ion donor, and a base as a hydrogen-ion acceptor

NH3(aq) + H2O(l) → NH4+(aq) + OH-(aq)

Hydrogen ion aceptor,

Bronsted-Lowry Base

Hydrogen ion donor,

Bronsted-Lowry Acid

Makes the solution basic

Conjugate Acids and Bases

A conjugate acid is the particle formed when a base gains a hydrogen ion

A conjugate base is the particle that remains when an acid has donated a hydrogen ion

A conjugate acid-base pair consists of two substances related by the loss or gain of a single hydrogen ion Acids have conjugate bases while bases have conjugate

acids

NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

Base Acid Conjugate Acid

Conjugate Base

conjugate acid-base pair

conjugate acid-base pair

HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq)Acid Base Conjugate

AcidConjugate

Base

conjugate acid-base pair

conjugate acid-base pair

A water molecule that gains a hydrogen ion becomes a positively charged hydronium ion H3O+

Water can both accept AND donate a hydrogen ion A substance that can act as both an acid and a

base is said to be amphoteric Amino Acids as an example – building block of protein

Lewis Acids and Bases Acids accept a pair of electrons during a reaction

while a base donates a pair of electrons Lewis acid – a substance that can accept a pair of

electrons to form a covalent bond Lewis base – a substance that can donate a pair of

electrons to form a covalent bond MUCH broader, more inclusive definition than any of

the othersNH3 + BF3 → NH3BF3

Identify the Lewis Acid and the Lewis Base in the above equation

H+ + H2O → H3O+

H+

Acid Base

Acid-Base Definitions ReviewType Acid Base

Arrhenius H+ producer OH- producer

Bronsted-Lowry H+ donor H+ acceptor

Lewis electron-pair acceptor electron-pair donor

Reactions of Acids/Bases (Arrhenius and B.L kinds) Single replacement Double replacement

Single Replacement Reactions

A + BC = AB + C A chemical change in which one element

replaces a second element in a compound Acids react strongly with most metals – reactivity

with metals used to be a common way to classify acids

Hydrogen from the acid is always the cation replaced by the metal

Examples:2K(s) + 2H2O(l) 2KOH(aq) + H2(g)2Al (s) + 6HNO3 (aq) 2Al(NO3)3 (aq) + 3H2(g)

Activity Series of Metals Notice that aluminum is higher on

the activity series of metals than hydrogen

A reactive metal will replace any metal listed below it in the activity series

2Al (s) + 6HNO3 (aq) 2Al(NO3)3 (aq) + 3H2(g)

Cu + HNO3 No reaction

Dec

reas

ing

reac

tivity

Single Replacement Reactions

2K(s) + 2H2O(l) 2KOH(aq) + H2(g)

2Al (s) + 6HNO3 (aq) 2Al(NO3)3 (aq) + 3H2(g)

Ca (s) + H2SO4 (aq) CaSO4 + H2(g)

Pt (s) + HCl (aq) N.R.2Na (s) + H2SO4 (aq) Na2SO4 + H2(g)

Practice Problems

Double Replacement ReactionsAB + CD = AC + BDThe ions of two compounds exchange

places in an aqueous solution to form two new compounds Often produce a precipitate, a gas, or molecular

compound such as water

Precipitation (forms a solid or gas as a product) Acid/Base (forms water as product); also known

as a neutralization reaction

Ca(OH)2(aq) + 2HCl(aq) CaCl2(aq) + 2H2O(l)

Reactions in Aqueous SolutionAcid-Base reactions Acids and bases react to form water and a

salt, a generic name for an ionic compoundOH NaCl(aq) HCl(aq) NaOH(aq) 2

OH (aq)Cl (aq)Na (aq)Cl (aq)H (aq)OH (aq)Na 2

H3PO4 + 3Fe(OH)2 Fe3(PO4)2 + 6H2O

H2SO4 + Ca(OH) 2 CaSO4 + 2H2O

OH (aq)H (aq)OH 2