H O N O R S C H E M I S T R Y

UNIT 9 - ACIDS AND BASES

Name the following acids:

HCl H2SO4 H2SO3 H2S

Name the following bases:

NaOH Ca(OH)2 Cu(OH)2 NH4OH

WARM UP 11/25: ACID/BASE NAMING

COMMON ACIDS

• Sulfuric Acid (H2SO4)• “battery acid”• Most commonly

produced industrial chemical in the world

• Nitric Acid (HNO3)• Volatile, unstable

liquid• Used in explosives• Turns proteins yellow

• Phosphoric Acid (H3PO4)• Used in fertilizers, animal

feed, soda, detergents• Hydrochloric Acid (HCl)

• “stomach acid”• Used in steel making &

food processing• Acetic Acid (HC2H3O2)

• “vinegar”• Used in food industry,

fungicides, plastics

COMMON BASES

• Sodium Hydroxide(NaOH)• “lye”• Drain cleaner, oven

cleaner, soap making• Potassium Hydroxide

(KOH)• Liquid soap, potash

• Magnesium Hydroxide(Mg(OH)2)• antacids

• Calcium Hydroxide(Ca(OH)2)• Slaked lime

• Ammonia Water (NH3)• Cleaning products

Strengths of Acids and Bases Video

PROPERTIES OF ACIDS

• Molecular compounds• Ionize in water H3O+1

• Corrosive to metals and skin (React with most metals to form hydrogen gas.)

• Taste sour (like lemons—citric acid) • pH less than 7 • Neutralizes bases producing salt and water • Electrolytes

PROPERTIES OF BASES

• Ionize in water OH-1

• Feel "slippery".• Taste bitter (like soap) • Electrolytes• Caustic• pH greater than 7. • Neutralizes acids producing a salt and

water.

SOME ACID/BASE INDICATORS

Acids:1. Blue litmus turns red2. Bromothymol blue turns yellow3. Phenolphthalein turns colorless/cloudy

Bases:1. Red litmus to blue2. Bromothymol blue turns blue3. Phenolphthalein turns hot pink

Can you tell which is which?

Sample drops here

PHENOLPTHALEIN

@ Wikimedia Commons, Public Domain

WHY ARE ACIDS & BASES ELECTROLYTES?

BECAUSE THEY PRODUCE IONS IN SOLUT ION

ACIDS AND BASES

IONIZATION EQUATIONS

• Acids• HBr(aq) + H2O(l) → H3O+(aq) + Br-(aq)

• Bases• NH3(aq) + H2O(l) → NH4

+(aq) + OH-(aq)

• Concentration: Amount of acid or base/amount of water or solution

• Strength: How well that particular acid or base ionizes (amount of H3O+1 or OH- )

• Strong acid/base: An acid/base that ionizes almost completely

• Weak acid/base: An acid/base that only partially ionizes

STRENGTH VS. CONCENTRATION

Strength of Acids and Bases Simulation

Strong WeakHCl H2SO4 HF CH3COOHHBr HClO3 H2S H2SO3HI HClO4 HNO2 H3PO4HNO3

LIST OF STRONG AND WEAK ACIDS

Organic acids: end in –COOH, weak acid

Ex: vinegar CH3COOH

Mem

oriz

e!!

Strong WeakGroup I and II metals with hydroxides

NH3 and any non-group I or II hydroxide

LIST OF STRONG AND WEAK BASES

TYPES OF ACIDS/BASESARRHENIUS & BRONSTED-LOWERY

ACID/BASE TYPE DEPENDS ON BEHAVIOR

Acid Behavior Base Behavior

Arrhenius Releases H+ in solution

Releases OH- in solution

Bronsted-Lowery Proton (H+) donor Proton (H+) acceptor

ARRHENIUS ACIDS/BASES

What happens when an Arrhenius acid and an Arrhenius base are mixed?

Acid produces H+Base produces OH-

Neutralization: H+(aq) + OH-

(aq) H2O(l)

General Equation: Acid + Base → Salt + Water

LiOH(aq) + HBr(aq) → LiBr(aq) + H2O(l)

What’s a salt? ionic compound formed from cation of a base (parent) & anion of an acid (parent)

ARRHENIUS ACIDS/BASES

Do neutralization reactions look familiar?

LiOH(aq) + HBr(aq) → LiBr(aq) + H2O(l)

Complete Ionic Eqn:

Net Ionic Eqn:

WRITE BALANCED EQNS FOR THE NEUTRALIZATION OF EACH OF THE

FOLLOWING A/B PAIRS:

• sodium hydroxide & hydrochloric acid

• calcium hydroxide & sulfuric acid

• potassium hydroxide & nitric acid

BRONSTED-LOWERY THEORY

During a Bronsted-Lowery acid/base reaction:

H+ is transferred from an acid to a base

HCl + NH3 → NH4+ + Cl-

Proton donor

Proton acceptor

VOCABULARY

• Monoprotic acid = only one ionizable H+

• Examples: HCl, HBr, HC2H3O2, HNO3

• Polyprotic acid = more than one ionizable H+

• Examples: H2SO4, H3PO4

• Amphoteric = substance that can act as an acid or a base• Example:• H2O + HCl → H3O+ + Cl-

• H2O + NH3 → NH4+ + OH-

BRONSTED-LOWERY CONJUGATE ACIDS & BASE

DEFINITIONS

• Conjugate Acid: formed when a Bronsted-Lowery base gains a H+

• Conjugate Base: formed when a Bronsted-Lowery acid loses a H+

HCl + NH3 → NH4+ + Cl-

Proton donor

Proton acceptor

conjugateacid

conjugate base

IDENTIFY A, B, CA, & CB

• NH3 + H3O+ → NH4+ + H2O

• CH3OH + NH2- → CH3O- + NH3

• OH- + H3O+ → H2O + H2O

• NH2- + H2O → NH3 + OH-

WRITE THE CONJUGATE BASE FOR EACH ACID BELOW.

• H3O+

• H2SO3

• HCO3-

• HOCl

• NH4+

WRITE THE CONJUGATE ACID FOR EACH BASE BELOW.

• I-

• SO3-2

• PO4-3

• C2H3O2-

• H2BO3-

WHICH IS STRONGER, PARENT ACID/BASE OR CONJUGATE?

PARENT ACID/BASE

• Pure water ionize slightly according to:

The product of molar concentrations of the ions is equal to a constant Kw.

= Kw

Kw = 1.00 * 10-14

AUTOIONIZATION OF WATER

11322

−+ +↔+ OHOHOHOH

][][ 113

−+ • OHOH

In a neutral solution:

In an acidic solution:

In a basic solution:

RELATIONSHIPS

7113 10*1][][ −−+ == OHOH

][][ 113

−+ > OHOH

][][ 113

−+ < OHOH

EXAMPLE PROBLEM

• What is the [OH-] in an aqueous solution if [H3O+] = 6.5 x 10-10 M?

pH and pOH Scales

[H+] M [OH-] M pH value

Acidic >1.0x10-7 <1.0X10-7 <7.00

Neutral =1.0x10-7 =1.0x10-7 =7.00

Basic <1.0x10-7 >1.0x10-7 >7.00

• A change in [H+] by a factor of 10 causes the pH to change by 1.

• Solution with a pH of 6 has 10x the [H+] as a solution with a pH of 7.

pH: measure of [H3O+1] in a solution, measure of “acidity”

pOH: measure of [OH-1] in a solution, measure of “alkalinity”

PH AND POH

Neutral0 7 14

Acid Base

Neutral0 7 14

Base Acid

pH Scale

1 42 53 6

IMPORTANT FORMULAS

]log[ 3+−= OHpH ]log[ 1−−= OHpOH

pHOH −+ = 10][ 3pOHOH −− = 10][ 1

14=+ pOHpH ]][[ 3−+= OHOHKW

PRACTICE PROBLEMS[H+] [OH-] pH pOH Soln Type

1.00 x 10-3 M

2.523

3.043.45 x 10-8 M

6.9 x 10-14 M

10.000

9.7

[H3O+1] =

FIND THE PH OF THE FOLLOWING:

a. 1.00 * 10-3 M d. 7.01 * 10-6 Mb. 1.00 * 10-6 M e. 9.47 * 10-8 Mc. 6.59 * 10-10 M f. 6.89 * 10-14 M

a. d.b. e.c. f.

pH =

FIND THE [H3O+1]

a. 3.000 d. 2.523b. 10.000 e. 6.149c. 6.607 f. 7.662

a. d.b. e.c. f.

pOH =

FIND THE PH FOR THE FOLLOWING:

a. 2.00 d. 4.976b. 7.00 e. 9.714c. 1.263 f. 3.004

a. d.b. e.c. f.

[OH-1] =

FIND THE PH FOR THE FOLLOWING:

a. 1.00 x 10-4 M d. 3.45 x 10-8 Mb. 1.00 x 10-6 M e. 4.97 x 10-10 Mc. 2.64 x 10-13 M f. 2.93 x 10-2 M

a. d.b. e.c. f.

FIND THE [H3O+1]

a. 1.00 * 10-4 M d. 3.45 * 10-8 Mb. 1.00 * 10-6 M e. 4.97 * 10-10 Mc. 2.64 * 10-13 M f. 2.93 * 10-2 M

a. d.b. e.c. f.

[OH-1] =

TITRATIONS

• An acid-base titration is a lab procedure used to determine the concentration of a solution by neutralizing it with a solution of known concentration.

• The moles of acid will equal the moles of base at the equivalencepoint.

Titration Technique Video

TITRATIONS

• Endpoint: When you actually stop doing the titration. This is determined by a color change in the indicator or an indication from a pH probe.

• Equivalence point: When the solution is neutralized& moles of H3O+ = molesOH-

• Indicator: weak acid or base and its conjugate ion, whose color changes with changes in pH

• Standard solution: solution of known concentration used as the titrant in a titration

TITRATION TERMS

TITRATION CURVES

On the following slide you will see 3 different curves.

The relationships are:Strong Acid titrated with Strong BaseWeak Acid titrated with Strong BaseStrong Acid titrated with Weak Base

Using those graphs compare the pH values of each substance as well as the equivalence points

TITRATION CURVES

TITRATION CURVES – WEAK ACID/STRONG BASE

TITRATION CURVES – WEAK BASE/STRONG ACID

DIPROTIC ACID TITRATION CURVE

BUFFERS

• Definition: weak acid/base & conjugate system that maintains pH when strong acid or base is added to the buffer• Example: Blood buffer HCO3

-/CO3-2

• How would a buffer affect the titration of an acid or base?• Much more titrant has to be added before

the pH changes significantly

BUFFERED TITRATION CURVE

TITRATIONS – EXAMPLE PROBLEMS

If 20.0 mL of 0.500 M NaOH to neutralize 25.0 mL of HCl, what is the concentration of the HCl?

If 27.4 mL of 0.0154 M Ba(OH)2 is used to titrate 20.0 mL of HCl, what is the concentration of HCl?

PRACTICE PROBLEM 1

How many milliliters of 0.0947 M NaOH are needed to neutralize 21.4 mL of 0.106 M HCl?

PRACTICE PROBLEM 2

If 26.4 mL of LiOH solution are required to neutralize 21.7 mL of 0.5M HBr, what is the concentration of the basic solution?

PRACTICE PROBLEM 3

What is the molar concentration of a 50.0 mL solution of NaOH that is titrated to an endpoint with 15.0 mL of a 0.00300 M solution of H2SO4?

PRACTICE PROBLEM 4

DILUTING SOLUTIONS

H2O12M

2M

Mole 1 = Mole 2

M=mol/volume ; mol= (M)(V)

(M1)(V1)=(M2)(V2) Key words – to dilute, diluted solution

DILUTING SOLUTIONS – PRACTICE PROBLEM

• What volume of 2.00M CaCl2 would you use to make 0.5L of 0.300M CaCl2?

STUDY TOPIC LIST

• Vocabulary/Definitions• Strong vs. Weak acids & bases• Acid/Base Properties• Uses of acids and bases• Nomenclature• Conjugate acids/bases• Neutralization reactions• pH/pOH/[H+]/[OH-]/Kw calculations• pH scale• Titration problems• Color changes of indicators (red & blue litmus paper,

phenolphthalein, bromothymol blue)• Titration curves• Buffers• Dilution problems• Arrhenius vs. Bronsted Lowery acid/base theories• Unit 8 Solutions material