11

The Chemistry of The Chemistry of Acids and BasesAcids and Bases

The Chemistry of The Chemistry of Acids and BasesAcids and Bases

22

33

Acid and BasesAcid and Bases

44

Acid and BasesAcid and Bases

VinegarVinegarAcetic AcidOr

Vinegar

Acetic AcidOr

Vinegar

Vinegar is a weak acidthat has many household uses

Vinegar is a weak acidthat has many household uses

55

Acid and BasesAcid and Bases

66

Acids

77

Dissociation of Acids

HNO3 (l) + H2O (l) H30+ (aq) + NO3- (aq)

H3O+ is called a hydronium ion

88

99

Some Properties of Acids

Produce H3O+ ions in water (the hydronium ion is a hydrogen ion

attached to a water molecule)

Taste sour

Reacts with a metal to produce hydrogen gas

Electrolytes

React with bases to form a salt and water

pH is less than 7

Turns blue litmus paper to red “Blue to Red A-CID”

1010

Naming Acids and Bases

A Review

1111

Anion Ending Acid Name

-ide hydro-(stem)-ic acid

-ate (stem)-ic acid

-ite (stem)-ous acid

Acid Nomenclature Review

Binary Binary

Ternary Ternary

An easy way to remember which goes with which…An easy way to remember which goes with which…

““In the cafeteria, youIn the cafeteria, you ATEATE somethingsomething ICICky”ky”

1212Acid Nomenclature Flowchart

h yd ro - p re fix-ic en d in g

2 e lem en ts

-a te en d in gb ecom es-ic en d in g

-ite en d in gb ecom es

-o u s en d in g

n o h yd ro - p re fix

3 e lem en ts

AC ID Ss ta rt w ith 'H '

1313

• HBr HBr (aq)(aq)

• HH22COCO33

• HH22SOSO33

hydrohydrobromicbromic acidacid

carboncarbonicic acidacid

sulfursulfurousous acidacid

Acid Nomenclature Review

1414

Name ‘Em!

HCl (aq)HCl (aq)

HI (aq)HI (aq)

H2SO4 (aq)H2SO4 (aq)

HNO2 (aq) HNO2 (aq)

HIO3 (aq) HIO3 (aq)

HydroHydrochlorchloricic acid acid HydroHydrochlorchloricic acid acid

HydroHydroiodiodicic acid acid HydroHydroiodiodicic acid acid

SulfurSulfuricic acid acid SulfurSulfuricic acid acid

NitrNitrousous acid acid NitrNitrousous acid acid

IodIodicic acid acid IodIodicic acid acid

1515

Bases

1616

Some Properties of Bases

Produce OHProduce OH-- ions in water ions in water

Taste bitter, chalkyTaste bitter, chalky

Are electrolytesAre electrolytes

Feel soapy, slipperyFeel soapy, slippery

React with acids to form salts and waterReact with acids to form salts and water

pH greater than 7pH greater than 7

Turns red litmus paper to blue “Turns red litmus paper to blue “BBasic asic BBlue”lue”

1717

Some Common Bases

NaOHNaOH sodium hydroxidesodium hydroxide lyelye

KOHKOH potassium hydroxidepotassium hydroxide liquid soapliquid soap

Ba(OH)Ba(OH)22 barium hydroxidebarium hydroxide stabilizer for plasticsstabilizer for plastics

Mg(OH)Mg(OH)22 magnesium hydroxidemagnesium hydroxide “MOM” Milk of magnesia“MOM” Milk of magnesia

Al(OH)Al(OH)33 aluminum hydroxidealuminum hydroxide Maalox (antacid)Maalox (antacid)

1818

Acid Base Theories

1919

Acid/Base definitions

• Definition #1: Arrhenius (traditional)

Acids – produce H+ ions which produce hydronium ion (H3O+) when dissolved in water.

Bases – produce OH- ions

(problem: some bases don’t have hydroxide ions!)

2020

2121Arrhenius acid is a substance that produces H+ (H3O+) in water

Arrhenius base is a substance that produces OH- in water

2222

Acid/Base Definitions

• Definition #2: Brønsted – Lowry

Acids – proton donor

Bases – proton acceptor

A “proton” is really just a hydrogen atom that has lost it’s electron!

2323

2424

A Brønsted-Lowry acid is a proton donorA Brønsted-Lowry base is a proton acceptor

acidacidbasebaseAccepts a Proton or H+

Accepts a Proton or H+

Donates a Proton or H+

Donates a Proton or H+

2525Acids & Base Acids & Base DefinitionsDefinitions

Lewis acid - a Lewis acid - a substance that substance that accepts an electron accepts an electron pairpair

Lewis base - a Lewis base - a substance that substance that donates an electron donates an electron pairpair

Definition #3 – Lewis Definition #3 – Lewis

2626

Lewis Acid/Base ReactionLewis Acid/Base Reaction

2727

pH Scale

2828

2929

The The pH scalepH scale is a way of is a way of expressing the strength of expressing the strength of acids and bases.acids and bases.

The The pH scalepH scale is a way of is a way of expressing the strength of expressing the strength of acids and bases.acids and bases.

Instead of using very small Instead of using very small numbers, we just use the numbers, we just use the NEGATIVE power of 10 on the NEGATIVE power of 10 on the Molarity of the HMolarity of the H33OO++ (or OH (or OH--) )

ion.ion.

Instead of using very small Instead of using very small numbers, we just use the numbers, we just use the NEGATIVE power of 10 on the NEGATIVE power of 10 on the Molarity of the HMolarity of the H33OO++ (or OH (or OH--) )

ion.ion.

pH under 7 = acidpH 7 = neutralpH over 7 = base

pH under 7 = acidpH 7 = neutralpH over 7 = base

3030

3131

pH of Common pH of Common SubstancesSubstances

3232Calculating the pH

pH = - log [H3O+](Remember that the [ ] mean Molarity)

Example: If [H3O+] = 1 X 10-10

pH = - log 1 X 10-10

pH = - (- 10)

pH = 10

Example: If [H3O+] = 1.8 X 10-5

pH = - log 1.8 X 10-5

pH = - (- 4.74)

pH = 4.7

3333

Try These!Try These!

Find the pH of these:Find the pH of these:

1)1) A 0.15 M solution of Hydrochloric acidA 0.15 M solution of Hydrochloric acid

Answer: pH = .82 Answer: pH = .82

2) A 3.00 X 102) A 3.00 X 10-7-7 M solution of Nitric acid M solution of Nitric acid

Answer: pH = 6.52Answer: pH = 6.52

3434pH calculations – Solving for pH calculations – Solving for HH33O+O+pH calculations – Solving for pH calculations – Solving for HH33O+O+

If the pH of Coke is 3.12, If the pH of Coke is 3.12,

what is the [Hwhat is the [H33OO++]?]?

Because pH = - log [HBecause pH = - log [H33OO++] then ] then

- pH = log [H- pH = log [H33OO++]]

Take antilog (10Take antilog (10xx) of both sides ) of both sides

*** to find antilog on your calculator, *** to find antilog on your calculator,

look for “Shift” or “2look for “Shift” or “2nd nd function” and then the log buttonfunction” and then the log button

[H[H33OO++] =] = 1010-pH-pH

[H[H33OO++] = 10] = 10-3.12-3.12 = 7.59 x 10 = 7.59 x 10-4-4 M M

(On your calculator: 2(On your calculator: 2ndnd, log, -3.12, enter), log, -3.12, enter)

3535You try thisYou try this

• A solution has a pH of 8.5. What is the A solution has a pH of 8.5. What is the molarity of hydronium (Hmolarity of hydronium (H33OO++) ions in ) ions in the solution?the solution?

- log [H- log [H33OO++] = pH ] = pH

- log [H- log [H33OO++] = 8.5] = 8.5

log [Hlog [H33OO++] = - 8.5] = - 8.5

antilog (log [H3O+]) = antilog (log [H3O+]) = Antilog -8.5Antilog -8.5

[H[H33OO++] = 10] = 10-8.5-8.5

[H[H33OO++] = 3.2 X 10] = 3.2 X 10-9 -9 MM

- log [H- log [H33OO++] = pH ] = pH

- log [H- log [H33OO++] = 8.5] = 8.5

log [Hlog [H33OO++] = - 8.5] = - 8.5

antilog (log [H3O+]) = antilog (log [H3O+]) = Antilog -8.5Antilog -8.5

[H[H33OO++] = 10] = 10-8.5-8.5

[H[H33OO++] = 3.2 X 10] = 3.2 X 10-9 -9 MM

3636pOH

• Since acids and bases are Since acids and bases are opposites, pH and pOH are opposites, pH and pOH are opposites!opposites!

• pOH does not really exist, but it is pOH does not really exist, but it is useful for changing bases to pH.useful for changing bases to pH.

• pOH looks at the perspective of a pOH looks at the perspective of a basebase

pOH = - log [OHpOH = - log [OH--]]Since pH and pOH are on opposite Since pH and pOH are on opposite

ends,ends,pH + pOH = 14pH + pOH = 14

3737

pH vs pOH Scale

• http://www.ausetute.com.au/phscale.html

3838

[H[H33OO++], [OH], [OH--] and pH] and pH

What is the pH of a 0.0010 M What is the pH of a 0.0010 M NaOHNaOH solution? solution?

pOH = - log 0.0010pOH = - log 0.0010

pOH = 3pOH = 3

pH = 14 – 3 = 11pH = 14 – 3 = 11

3939

Strong and Weak

Acids and Bases

4040

4141

H2SO4, HNO3, HCl, HBr, HI, and HClO4 are among the only known strong acids.

Strong and Weak AcidsStrong and Weak Acids

The strength of an acid is determined by the amount of IONIZATION or DISSOCIATION when put in water.

The strength of an acid is determined by the amount of IONIZATION or DISSOCIATION when put in water.

4242

The strength of an base is determined by the amount of IONIZATION or DISSOCIATION when put in water.

• NaOH (aq) ---> NaNaOH (aq) ---> Na+ + (aq) + OH(aq) + OH- - (aq)(aq)

Strong and Weak BasesStrong and Weak Bases

Strong bases include Strong bases include KOH, NaOH, RbOH, KOH, NaOH, RbOH, CsOH, Ca(OH)CsOH, Ca(OH)22, Sr(OH), Sr(OH)22, ,

and Ba(OH)and Ba(OH)22

4343

Ways to find pH

4444Finding the pH

Paper testsPaper tests

Litmus paperLitmus paper

Blue to red is “a-cid”Blue to red is “a-cid”

Red to blue is base Red to blue is base

pH paperpH paper

Turns various colorsTurns various colors

according to the pHaccording to the pH

4545

Finding the pHpH MeterpH MeterTests the voltage of the Tests the voltage of the

electrolyteelectrolyte

Converts the voltage to pHConverts the voltage to pH Very cheap, accurateVery cheap, accurate

Must be calibrated with a Must be calibrated with a buffer solutionbuffer solution

4646pH indicators

• Indicators are dyes that can be added that will change color in the presence of an acid or base.

• Some indicators only work in a specific range of pH

• Once the drops are added, the sample is ruined

• Some dyes are natural, like radish skin or red cabbage

4747

Titration

4848Setup for titrating an acid with a baseSetup for titrating an acid with a base

4949

TitrationTitrationTitrationTitration

1. Add solution from the buret.1. Add solution from the buret.2. Reagent (base) reacts with 2. Reagent (base) reacts with

compound (acid) in solution compound (acid) in solution in the flask.in the flask.

3.3. Indicator shows when exact Indicator shows when exact neutralization reaction has neutralization reaction has occurred. (Acid = Base)occurred. (Acid = Base)

This is called This is called NEUTRALIZATION.NEUTRALIZATION.

5050

Does this look familiar?Does this look familiar?

MM11 • V • V11 = M = M22 • V • V22

Finding Molarity by Finding Molarity by TitrationTitration

Finding Molarity by Finding Molarity by TitrationTitration