Unit 13Unit 13

Acids and BasesAcids and Bases

Properties

• electrolyte

• turn litmus red

• sour taste• slippery feel

• turn litmus blue

• bitter taste• sticky feel

• electrolyte

• react with bases to form water and a salt (ionic compound)

• react with acids to form water and a salt (ionic compound)

ACIDS: Most citrus fruits, tea, battery acid, vinegar, milk, soda, apples.

BASES: Common household bases include baking soda, lye, ammonia, soap, and antacids.

.

Examples

Indicators

• Indicators are substances that change color in the presence of an acid or a base– Indicators are made up of weak acids or weak

bases– Examples of indicators include pH paper, red and

blue litmus paper, and phenolphthalein

Acids Affect Indicators:

Blue litmus paper turns red in contact with an acid. It remains blue when in contact with a base or neutral solution.

Bases affect indicators:

Red litmus paper turns blue in contact

with a base. It remains red when in contact with an acid or neutral solution.

Phenolphthalein turns pink in a

base. It is colorless in an acid or

neutral solution.

Definitions• There are 3 definitions used to

describe acids and bases:• Arrhenius

• BrØnsted-Lowry

• Lewis

• The most traditional is Arrhenius acids and bases.

Definitions

• ArrheniusArrhenius - In aqueous solution… - In aqueous solution…

HCl + H2O H+ + Cl–

– AcidsAcids form hydrogen ions (H+)

H

HH H H

H

ClClO O

–+

acid

Also called hydronium ions (H3O+)

Definitions

• ArrheniusArrhenius - In aqueous solution… - In aqueous solution…

– BasesBases form hydroxide ions (OH-)

NH3 + H2O NH4+ + OH-

H

H

HH H

H

N NO O–+

H

H

H H

base

Definitions

• Brønsted-LowryBrønsted-Lowry

HCl + H2O Cl– + H3O+

– AcidsAcids are proton (H+) donors. – BasesBases are proton (H+) acceptors.

conjugate acidconjugate basebaseacid

• ..

Conjugate acid – particle formed when a base gains a H+

Conjugate base – particle that remains when an acid has donated a H+

Another common way to refer to hydrogen ions is to call them

“protons”

Definitions

• LewisLewis– AcidsAcids are electron pair acceptors. – BasesBases are electron pair donors.

Lewis base

Lewis acid

White Board Questions1. When you wafted a substance your nose

burned. Would this substance be an acid or a base?

2. A hydrogen ion (H+) can also be called a _________ or ____________.

3. Arrhenius acids are compounds that break up in water to give off _____________.

4. What color litmus paper would you use to test an acid? What color will it turn?

5. If your food tastes bitter, which do you think it could possibly be an acid or a base?

ACID

H+

H3O+Proton

Blue turns red

BASE

White Board Questions6. A BrØnsted-Lowry base _________ hydrogen

ions.

7. Phenolphthalein turns pink when it comes in contact with a(n) _________.

8. Which of the scientists defined the typical acid?

9. If you are eating and it has a sour taste, would that be an acid or a base?

10. If a piece of red litmus paper turns blue than it is a(n) ___________.

accepts

base

Arrhenius

acid

base

Naming Acids

• Binary acids

– Contains 2 different elements: H and another

– Always has “hydro-” prefix

– Root of other element’s name

– Ending “-ic”

Examples of Binary Acids

• HI is hydroiodic acid

• H2S is hydrosulfuric acid

• HBr is hydrobromic acid

• HCl is hydrochloric acid

Naming Acids

• Ternary Acids - Oxyacids

– Contains 3 different elements: H, O, and another

– No prefix

– Name of polyatomic ion (p. 147)

– Ending “–ic” for polyatomic ion ending in “-ate” and “–ous” for ion ending in “-ite”

Examples of Ternary Acids

• ClO3 is chlorate so HClO3 is chloric acid

• PO4 is phosphate

so H3PO4 is phosphoric acid

• PO3 is phosphite

so H3PO3 is phosphorous acid

• NO2 is nitrite HNO2 is nitrous acid

• NO3 is nitrate HNO3 is nitric acid

Naming Acids cont.

• HC2H3O2 or CH3COOH

Name is acetic acid

Common name = vinegar

Practice Naming Acids

• H2SO3

– Sulfurous acid

• HF

– Hydrofluoric acid

• H2Se

– Hydroselenic acid

• Perchloric acid

– HClO4

• Carbonic acid

– H2CO3

• Hydrobromic acid

– HBr

Ion Product of WaterSelf- ionization of water – the simple dissociation of water

H2O H+ + OH-

Concentration of ea. ion in pure water: [H+] = 1.0 x 10-7M + [OH-] = 1.0 x 10-7M

Ion-product constant for water (Kw), Where KWhere Kww = 1.0 x 10 = 1.0 x 10-14-14

KKww = [H = [H++] [OH] [OH--]]

Acid [H+] > [OH-] Base [H+] < [OH-]

Neutral [H+] = [OH-]

Calculating [H+] and [OH-]

• reverse the pH equation

• The pH of a solution is 8. Find the [H+] and [OH-] and determine whether it is acidic, basic, or neutral.

– basic

[H+] = 1 x 10-pH and [OH-] = 1 x 10-pOH

[H+] = 1 x 10-8 M [OH-] = 1 x 10-(14-8) M = 1 x 10-6 M

Examples1. If the [H+] in a solution is 1.0 x 10-5M, is the

solution acidic, basic or neutral?

1.0 x 10-5 M

What is the concentration of the [OH-]?Use the ion-product constant for water (Kw):

Kw = [H+] [OH-] 1.0 x 10-14 = [1.0 x 10-5] [OH-] 1.0 x 10-14 = [OH-] 1.0 x 10-5

1.0 x 10-(14-5)

pH 5 = acidic

1.0 x 10-9 M

Examples2. If the pH is 9, what is the concentration of

the hydroxide ion?

Kw = [H+] [OH-]

1.0 x 10-14 M = [1.0 x 10-9M] [OH-]

1.0 x 10-5 M = [OH-]

3. If the pOH is 4, what is the concentration of the hydrogen ion?

Kw = [H+] [OH-]

1.0 x 10-14 M = [H+] [1.0 x 10-4 M]

1.0 x 10-10 M = [H+]

14 = pH + pOH

14 = 9 + pOH

5 = pOH

14 = pH + pOH

14 = pH + 4

10 = pH

Examples4. A solution has a pH of 4. Calculate the pOH,

[H+] and [OH-]. Is it acidic, basic, or neutral?

14= pH + pOH

14= 4 + pOH

10= pOH

–Acidic since pH is 4

M101][OH 10

M4101][H

Practice Problems:

Classify each solution as acidic, basic or neutral.

1. [H+] = 1.0 x 10-10 M

2. [H+] = 0.001M

3. [OH-] = 1.0 x 10-7 M

4. [OH-] = 1.0 x 10-4 M

Basic pH 101.0 x 10-3 acid pH 3

Neutral14=pH+4 base pH 10

[OH-] pOH pH [H+]

1 x 10-14 14 0 1 x 100

1 x 10-13 13 1 1 x 10-1

1 x 10-12 12 2 1 x 10-2

1 x 10-11 11 3 1 x 10-3

1 x 10-10 10 Increasing acidity 4 1 x 10-4

1 x 10-9 9 5 1 x 10-5

1 x 10-8 8 6 1 x 10-6

1 x 10-7 7 Neutral 7 1 x 10-7

1 x 10-6 6 8 1 x 10-8

1 x 10-5 5 9 1 x 10-9

1 x 10-4 4 Increasing basicity 10 1 x 10-10

1 x 10-3 3 11 1 x 10-11

1 x 10-2 2 12 1 x 10-12

1 x 10-1 1 13 1 x 10-13

1 x 100 0 14 1 x 10-14

White Board Practice Fill in the chart.

[OH-] pOH pH [H+]

8

1x 10-12

10

1 x 10-3

1.0 X 10 -8

1.0 X 10 -2

1.0 X 10 -4

1.0 X 10 -6

1.0 X 10 -10

1.0 X 10 -11

6

3 11

4

2 12

Fill in the chart.

[OH-] pOH pH [H+]

8

1x 10-12

10

1 x 10-3

5

1 × 10-1

1.0 X 10 -8

1.0 X 10 -2

1.0 X 10 -4

1.0 X 10 -6

1.0 X 10 -10

1.0 X 10 -11

6

3 11

4

2 12

9

113

1.0 X 10 -5 1.0 X 10 -9

1.0 X 10 -13

Strength or Concentration

• Strong Acid/BaseStrong Acid/Base– Ionize completely in water– strong electrolyte

- +

Acids

HCl

HNO3

H2SO4

HBr

HI

HClO4

Bases

NaOH

KOH

Ca(OH)2

Ba(OH)2

Strength or Concentration

• Weak Acid/BaseWeak Acid/Base– ionize partially in water– weak electrolyte

- +

Acids

HF

CH3COOH

H3PO4

H2CO3

HCN

Base

NH3

Strength or Concentration

• How strong or weak an acid or base is, depends on its degree of ionization.

- + - +

pH = -log[H+]

pH Scale

0

7INCREASING

ACIDITY NEUTRALINCREASING

BASICITY

14

pouvoir hydrogène (Fr.)“hydrogen power”

pH is the negative logarithm of the hydrogen ion concentration

The pH Scale

pH Scale

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

pH formulas

pH = -log[H+]

pOH = -log[OH-]

pH + pOH = 14

Neutralization

• Chemical reaction between an acid and a base.

• Products are a salt (ionic compound) and water.

Neutralization

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

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

HCHC22HH33OO22 + NaOH + NaOH NaC NaC22HH33OO22 + H + H22OO

– Salts can be neutral, acidic, or basic.

– Neutralization does not mean pH = 7.

weak

strong strong

strong

neutral

basic

Titration

• TitrationTitration– Analytical method in

which a standard solution is used to determine the concentration of an unknown solution.

standard solution

unknown solution

• Equivalence point Equivalence point (endpoint)(endpoint)– Point at which equal amounts of H+

and OH- have been added.– Determined by…

• indicator color change

Titration cont.

• dramatic change in pH

Titration formula

moles H+ = moles OH-

MV n = MV n

M: MolarityV: volumen: # of H+ ions in the acid

or OH- ions in the base

Titration example

• 42.5 mL of 1.3M KOH are required to neutralize 50.0 mL of H2SO4. Find the molarity of H2SO4.

H2SO4

M = ?V = 50.0 mLn = 2

KOH

M = 1.3MV = 42.5 mLn = 1

MVn = MVnM(50.0mL)(2)=(1.3M)(42.5mL)(1)

M = 0.55M H2SO4

M= 55.25 100

Review of Acid and Base Definitions

• ArrheniusMost specific/exclusive definition

Created by Svante Arrhenius, Swedish

Acid: compound that creates H+ in an aqueous solution

HNO3 H+ + NO3-

Base: compound that creates OH- in an aqueous solution

NaOH Na+ + OH-

Review of Acid and Base Definitions

• Bronsted-LowryMore general definition than Arrhenius definition

Most commonly used definition

Created by 2 scientists around the same time (1923)

Acid: Molecule or ion that is a proton (H+) donor

HCl + H2O H3O+ + Cl-

Base: Molecule or ion that is a proton (H+) acceptor

NH3 + H2O NH4+ + OH-

Review of Acid and Base Definitions

• LewisMost general definition

Defined by electrons and bonding rather than H+

Created by the same scientist who electron-dot diagrams are named after

Acid: atom, ion, or molecule that accepts an electron pair to form a covalent bond

NH3 + Ag+ [Ag(NH3)2]+

Base: atom, ion, or molecule that donates an electron pair to form a covalent bond

BF3 + F- BF4-