Binary acids – use the prefix “hydro” + the name of the negative (second ion), changing the ending to “-ic acid”.Oxy-acids – Name the polyatomic ion, change the ending to either “-ic acid” or “-ous acid” according to the “ate = ic, ite = ous” rule.

HCl (aq) hydrochloric acid HBr (aq) hydrobromic acid HI (aq) hydroiodic acid HF (aq) hydrofluoric acid H2S (aq) hydrosulfuric acid

H2SO4 sulfuric acid

H2SO3 sulfurous acid

H3PO4 phosphoric acid

H3PO3 phosphorous acid

HNO3 nitric acid

Acids and Bases

What is an Acid? Base?

What do you think and acid is?

What do you think a base is?

Properties of Acids and Bases! Acids have specific properties

Sour taste pH beow 7.00 S.U. Turn litmus paper red Dissolve metals

Bases have similar properties Bitter taste pH above 7.00 S.U. Feel slippery Turn litmus paper blue

What else can they do?

Acids and bases neutralize each other In other words, they raise/lower the pH to a

non-acid/non-base

Acids and Bases can both destroy human tissue

How do they do that?

Acids and bases are electrolytes The ions that they produce give them their

properties

Strength of Acids

A strong acid is one that dissolves completely in solution. A weak acid is one that does not dissolve

completely.

Why would an acid not dissolve completely?

Do you know any acids or bases?

List some common acids and bases Vinegar is Acetic Acid Ammonia is a Base Sodium Bicarbonate (Baking soda) is a Base Batteries contain Sulfuric Acid Your stomach contains Hydrochloric Acid!

There are more than one

There are 3 different types of acids and bases Arrhenius Brönsted-Lowry Lewis

Arrhenius Acids and Bases

An Arrhenius Acid is a substance that releases H3O+ ions in an aqueous solution HCl H2O H3O+ + Cl-

An Arrhenius Base is a substance that releases –OH in an aqueous solution NaOH H2O Na+ + OH-

Brönsted-Lowry Acids and Bases

A Brönsted-Lowry acid is any species that can donate a proton (H+ ion) to another species; a proton donor

A Brönsted-Lowry base is any speices that can accept a proton (H+ ion) from another species; a proton acceptor

HCl + H2O H3O+ + Cl-

Which is the Brönsted-Lowry acid/base? Acid is the proton donator Base is the proton acceptor

HCl is the acid H2O is the base

Water: Acid or Base?

Take a look at these two reactions

1. NH3 + H2O NH4+

+ OH-

2. HCl + H2O H3O+ + Cl-

In reaction #1, which is the B-L acid? Base? Water is the acid and ammonia is the base

In reaction #2? HCl is the acid and water is the base

Amphiprotic

A compound that can be both a proton donor OR a proton acceptor in separate reactions is called amphiprotic or amphoteric

Lewis Acids and Bases

A Lewis Acid is any species that can accept a pair of electrons from another species; electron pair acceptor

A Lewis Base is any species that can donate a pair of electrons from another species; electron pair donor

Remember Lewis Structures!

Let’s look at a few examples

H+ H+ is an electron pair acceptor

:Ö-H- OH- is an electron pair donor

:Ö-H Lewis acid-base product

..

H

..

Compare the Definitions

Acid Base Acid Base Acid BaseReleases H

+

Releases O

H-

Proton donor

Proton acceptor

Electron pair acceptor

Electron pair donor

LewisBrönsted-LowryArrhenius

Acid-Base Equilibria

In a chemical reaction involving both acids and bases, dynamic equilibrium can still be achieved

A species that is an acid in the forward direction, can become the base in the reverse direction

HNO2 + H2O H3O+ + NO2-

acid base acid base

Let’s take a look at this reaction HNO2 donates a proton in the forward reaction

and is therefore a B-L acid H2O accepts a proton in the forward reaction

and is the B-L base In the reverse direction, H3O+ donates a

proton; B-L acid And NO2

- accepts a proton; B-L base

Conjugate Pairs

When an acid donates a proton, it becomes a conjugate base

When a base accepts a proton, it becomes a conjugate acid

Why? The acid-base reaction can be a reversible

reaction and so when you move in the opposite direction, the compounds are redefined as acids and/or bases

Conjugates

For example, look at the following reaction

HCl + H2O H3O+ + Cl-

Which reactant is the acid? The base? Now, in the reverse direction, which product

is the acid? The base? Now, what are the conjugate pairs?

Conjugates, some more

Look at this reaction:NH3 + H2O NH4

+ + OH-

Which reactant is the acid? The base? Now, in the reverse direction, which product

is the acid? The base? Now, what are the conjugate pairs?

Conjugate Practice

What are the conjugate pairs for the following reactions?

HNO3 + OH- H2O + NO3-

HNO3 is the acid and NO3- is the conjugate base

OH- is the base and H2O is the conjugate acid

H2SO4(aq) + SO32-(aq) HSO4

-(aq) + HSO3-(aq)

Sulfuric acid is the acid and HSO4- is the conjugate

base Sulfite ion is the base and HSO3

- is the conjugate acid

Strength

If a acid is strong, then the conjugate base is weak and vice-versa

Strong/Weak Electrolytes

An electrolyte is a solution that will conduct an electrical current.

Any ionic compound that dissociates in solution will conduct electricity.

If a substance dissociates 100%, it is called a strong electrolyte.

A weak electrolyte dissociates < 100% (usually < 5%)

Strong Acids

Binary acids: HCl, HBr, and HI are strong acids. All other

binary acids are weak.

Oxy acids: If the number of oxygen atoms exceed the

number of hydrogen atoms by 2 or more, the acid is strong.

Strong Bases

Hydroxides made from metals in group 1 or group 2 are strong bases.

All other hydroxides are weak bases.

Molecular Structure and the Strength of Acids The strength of an acid depends on a number

of factors, such as the properties of the solvent, the temperature, and the molecular structure of the acid.

We compare the strengths of two acids, in the same solvent and at the same temperature. That way we can focus on the structure of the acid.

Binary Hydrides

HA ---> H+ + A- Two factors influence the extent to which the

acid undergoes ionization. One is the strength of the H-A bond

the stronger the bond, the more difficult it is for the HA molecule to break up and hence the weaker the acid.

Polarity versus Strength

The other factor is the polarity of the H-A bond. The difference in electronegativities between

H and A results in a polar bond. If the bond is highly polarized, it is a stronger

acid.

Hydrohalic Acids

The halogens form a series of binary acids called the hydrohalic acids.

The strengths of the hydrohalic acids increase in the following order: HF<<HCl<HBr<HI

Other Non-metallic Acid Strengths

In any vertical column (Group) of nonmetallic elements, there is a tendency toward increasing acidity of the hydride with increasing atomic number (as you go down the group).

For example, among the group VIA elements the acid strength increases in the order: H2O< H2S<H2Se<H2Te

Oxyacids

Many common acids contain one or more O-H bonds.

Practice Problems

1. HF

weak

2. H2S

weak

3. H2SO4

strong

4. H2CO3

weak

5. Fe(OH)3

weak

6. Barium hydroxide

strong

7. Chloric acid

strong

8. Sulfurous acid

weak

9. Hypochlorous acid

weak

10. Tin(IV) hydroxide

weak

Ba(OH)2

HClO3

H2SO3

HClO

Sn(OH)4

Review

In the following equations, name the acid and base. What was your justification? NH3 + H2O NH4

+ + OH-

2NaBr + H2SO4 Br2 + SO2 + 2NaOH

Review

What is the difference between a strong acid and a weak acid?

A buffer is a solution made from a weak acid and it’s conjugate base that neutralizes a small amount of acids or bases added to it

Calculating pH

pH

pH is a measure of how acidic, neutral or basic a solution is

The scale for pH is 0-14 7 is neutral 0-7 is acidic 7-14 is basic

The Numbers mean . . .

pH + pOH = 14 S.U.

pH = -log10[H3O+]

pOH = -log10[OH-]

What is pH?

The term pH refers to a scale that describes how strongly acidic or basic a solution is pH + pOH = 14 Acidic = 0-7 Neutral = 7 Basic = 7-14

The Kw Constant

Kw = 1.0 x 10-14

at standard thermodynamic temperature (25oC or 298 K)

Ionization Constants of Acids and Bases HA(aq) + H2O(l) ↔ H3O+(aq) + A-(aq)

Keq= [H3O+][A-] / [HA][H2O]

In a dilute solution, the concentration of water is constant, so

Keq= [H3O+][A-] / [HA]

Ionization Constants

The Ionization Constant for water; Kw is derived as follows:

First: for the acids

HA(aq) + H2O(l) H3O+(aq) + A-(aq)

Keq = Ka = [H3O+][A-] / [HA]

Now the bases . . .

B(aq) + H2O(l) BH+(aq) + OH-(aq)

Keq = Kb = [BH+][OH-] / [B]

Combine the two

HA(aq) + H2O(l) H3O+(aq) + A-(aq)

Keq = Ka = [H3O+][A-] / [HA]

&

B(aq) + H2O(l) BH+(aq) + OH-(aq)

Keq = Kb = [BH+][OH-] / [B]

=

Kw= [H3O+][OH-]

Calculations

Problem:What are the hydronium and hydroxide ion

concentrations in a 0.10M HCl?

HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq)

Kw = [H3O+][OH-]

1.0 x 10-14 = (0.1M) x [OH-]

[OH-] = 1.0 x 10-13

Calculating pH

A pH is equal to the -log10 of the Hydronium ion concentration

pH = -log10[H3O+]

If an acid has a [H3O+] of 1.0 x 10-2M; then the pH is 2 S.U.

S.U. = standard unit

Calculating [H3O+]

The concentration of Hydronium ions can be determined by the reverse calculation, sort of If the pH of a solution is 5.05 S.U., then the

concentration of [H3O+] is 10-pH. 5.05 S.U. = 10-5.05 = 8.9 x 10-6 M

Tricks

If your concentration is 1.0 x 10-10 M, then your pH will be 10 S.U.! The negative exponent becomes the pH

If your concentration is greater than 1.0, then the pH will be less than the negative exponent. 2.5 x 10-10 M = >10 S.U. = 9.6

This comes in handy when you are answering multiple choice questions about the pH of a solution.

Practice Problems

What is the pH of a solution if the [H3O+] is 5.0 x 10-3M?

What is the pH of a solution if the [OH-] is 2.0 x 10-3M?

What is the [H3O+] of a solution whose pH is 3.3?

What is the [OH-] of a solution whose pH is 8.1?

Arrhenius Neutralization Reaction

An Arrhenius acid-base reaction looks something like this (does it kind-a look familiar?

HCl + NaOH

HCl + NaOH H2O + NaCl

Neutralization Reactions

Any acid-base reaction is called a neutralization reaction. By products are always a salt, water (or a

gas). Heat is also generated These reactions can be violent

Predict the Products

HNO3 + KOH KNO3 + HOH

HBr + NH4OH NH4Br + HOH

H3PO4 + Ca(OH)2 Ca3(PO4)2 + HOH

H2SO3 + LiOH Li2SO3 + HOH

How do you measure pH?

Litmus Paper Color change indicator pH meter

Compare the Scale

pH [H3O+] [OH-] pOH 0 1 x 10-0 M 1 x 10-14 M 14 1 1 x 10-1 M 1 x 10-13 M 13 2 1 x 10-2 M 1 x 10-12 M 12

Acid & Base Indicators

Acid and Base indicators are substances that change color in response to a specific pH

Different indicators are used depending on the range of the sample

Comparison Chart

Indicator Color at pH 4.6 Color at pH 7.9 Methyl orange Yellow Yellow Bromothymol blue Yellow Blue Thymol blue Yellow Yellow

Which of these indicators can be used to distinguish between a solution whose pH is 4.6 S.U. and one that is 7.9 S.U.?

Look at the chart. Only Bromothymol blue can distinguish between the two solutions.

Comparison Chart

Indicator Transition Range of pH

Color Change

Methyl orange 3.2 – 4.4 Red to Yellow Bromothymol blue 6.0 – 7.6 Yellow to Blue Thymol blue 8.0 – 9.6 Yellow to Blue Phenolphthalein 8.2 – 10 Colorless to Pink Bromocresol green 3.8 – 5.4 Yellow to Blue Litmus 5.5 – 8.2 Red to Blue

Which indicators can be used to distinguish between Soln. A: pH = 2.0 and Soln. B pH = 5.0?

Methyl orange

Comparison Chart

Indicator Transition Range of pH

Color Change

Methyl orange 3.2 – 4.4 Red to Yellow Bromothymol blue 6.0 – 7.6 Yellow to Blue Thymol blue 8.0 – 9.6 Yellow to Blue Phenolphthalein 8.2 – 10 Colorless to Pink Bromocresol green 3.8 – 5.4 Yellow to Blue Litmus 5.5 – 8.2 Red to Blue

Which indicators can be used to distinguish between Soln. A: pH = 5.0 and Soln. B pH = 9.0?

Bromothymol blue or litmus

Titrations

Titration The process, operation, or method of determining the concentration of a substance in a solution to which the addition of a reagent having a known concentration is made in carefully measured amounts until a reaction of definite and known proportion is completed, as shown by a color change or by electrical measurement, and then calculating the unknown concentration.

The equivalence point (end point) is reached when a titrant is added and is stoichiometrically equal to the amount of moles of substance (known as analyte) present in the sample; or, the smallest amount of titrant that is sufficient to fully neutralize or react with the analyte

Titrations

NaVa = NbVb

(look familiar?) N is normality N = M x n (the number of moles of H+ or OH- ions

released into solution)

The titrant is usually the solution of known concentration that is delivered by a burette into a known quantity of the solution of unknown concentration

The titraver is the indicating solution

Naming Acids

Acids are formed when a Hydrogen is added to an anion

Take the anion root, 1. Add a hydro- in front2. Change the ending from –ide or -ate to –ic;

or from –ite to -ous3. Put them all together and add the word

“acid”

HCl

Take the anion root, 1. Add a hydro- in front

Hydro

2. Change the ending from –ide or –ate to –ic; or from –ite to -ous

chloride chloric

3. Put them all together and add the word “acid” Hydrochloric Acid

Acid/Base Nomenclature

Arrhenius Theory Binary Acids:

Prefix = hydro--hydro-- Suffix = --ic--ic

Examples:

HClHydroHydrochloricic acid

HBrHydroHydrobromicic acid

Acid/Base Nomenclature

Arrhenius Theory Oxy acids:

H+ combined with a polyatomic anion containing oxygen (P.178)

No prefix If the name of the anion ends –ate, the

acid ends –ic If the name of the anion ends –ite, the

acid ends -ous

Oxy Acid Examples

Ion Acid

SO4-2 H2SO4

Sulfate Sulfuric acid

NO3- HNO3

Nitrate Nitric acid

NO2- HNO2

Nitrite Nitrous acid

CO3-2 H2CO3

Carbonate Carbonic acid

Acid/Base Nomenclature

Arrhenius Theory Bases:

Name the hydroxide base.

Naming Bases

Bases are MUCH easier to name

Simply name the cation and anion NaOH Sodium hydroxide

Practice Problems

1. HF

hydrofluoric acid

2. H2S

hydrosulfuric acid

3. H2SO3

sulfurous acid

4. NaOH

Sodium hydroxide

5. Fe(OH)3

Iron (III) hydroxide

6. Calcium hydroxide

Ca(OH)2

7. Chromic acid

H2CrO4

8. Phosphorous acid

H3PO3

9. Acetic acid

HC2H3O2

10. Hydroselenic acid

H2Se

Homework Quiz: p. 538 #1-13

1. What are the observable properties of an acid?

2. What is an Arrhenius definition of a base?

3. How does a strong acid differ from a weak acid?

4. How does the definition of a Bronsted-Lowry definition of an acid differ from that of the Arrhenius definition?