Acid/base Definitions. Acid/Base Definitions. Acid / Base Chemistry. Acid/Base Definitions. Identifying Acids and Bases

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Identifying Acids and Bases

Acids

Acid (anhydrides)

Bases

Base (anhydrides)

Salts

contains H+ ions as the cation, with and other element as the anion

Non-metal oxide Contains OH- as the anion Combined with a cation A metal with oxygen

Ionic compound Formed from a cation and an anion

Metal and non-metal

H2SO4

HI P2O5 Ca(OH)2

Al2O3

Mg F2

KCl LiBr

Acid/base Definitions

•Arrhenius:

Acids: Any substance which releases H+ion in water solution.

Bases: Any substance which releases OH-ion in water solution.

Acid/Base Definitions

•Bronsted - Lowry:

Acids: Any substance which donates a proton.

Bases: Any substance which accepts a proton.

Acid/Base Definitions

•Lewis:

Acids: Any substance which can accept an electron pair.

Bases: Any substance which can donate an electron pair.

Acid / Base Chemistry

•Hydrogen ion concentration = [H+]

•Hydroxide ion concentration = [OH-]

•Pure H20 – neutral substance – – ph=7 and [H+]=[OH-]

•H2O will self-dissociate – H0 > H++ OH-

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Acid / Base Chemistry

- Kw- is the ion product constant for water

- Kw= 1.0 x 10-14M2 Kw= [H+] [OH-]

FOR H2O:Kw= [1.0 x 10-7M][1.0 x 10-7M]

-

there is an indirect relationship between [H+] and [OH-]

Acid / Base Chemistry

•Calculate [OH

-

] if [H

+

] is 1.0 x 10

-2

M

• Kw= [H+] [OH-]

• [OH

-

]= K

w

= 1.0 x 10

-14

M

2

• [H

+

] 1.0 x 10

-2

M

• [OH

-

]= 1.0 X 10

–12

M

Acid / Base Chemistry

•Calculate [H+] if [OH-] is 6.5 x 10-11M

• Kw= [H+] [OH-]

• [H+]= Kw = 1.0 x 10-14M2 [OH-] 6.5 x 10-11M

• [H+]=

• [H+] will tell us if a soln is acidic or basic.

Acidic solutions

Neutral solutions

Basic solutions

pH= 1- 6

[H+]= 1.0 x 10 M – 1.0 x 10 M [H+] > [OH-]

-1 -6

pH= 7 [H+] = [OH-]

1.0 x 10 M for both-7

pH= 8 -14

[H+]= 1.0 x 10 M – 1.0 x 10 M [H+] < [OH-]

-8 -14

Acid / Base Chemistry

• If [H+]= 1.0 x 10-9M, will the solution be basic or acidic?

• Basic

• Why?

• because the pH= 9 and this solution contains less [H+] than [OH-]

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Acid / Base Chemistry

• If [OH-]= 2.63 x 10-4M, will the solution be basic or acidic or neutral?

• Why?

Acid / Base Formulas

• pH= -log [H+]

• pOH= -log [OH-]

• pH + pOH =14

• [H+] = antilog (-pH)

• [OH-] = antilog (-pOH)

• How to use the calculator!!

• Calculate the pH of a solution with [H+] = 0.001 M. Is this acidic, basic, or neutral?

Acid / Base Formulas

• Calculate the pH of a solution with [OH-] = 7.9 x 10-3M. Is this acidic, basic, or neutral?

• Calculate the pH of a solution with [H+] = 4.2 x 10-6M. Acidic, basic, or neutral?

What is the [OH-]?

Acid / Base Formulas

• A solution with a pH of 9.1 has what [H+]?

– 2ndlog –9.1 ENTER

• What is the [OH-]?

• What is the pOH?

Acids, Bases, and Their Conjugates

•Water is amphoteric – has basic + acidic properties.

•Conjugate Acid: Substances formed in a reaction when a base gains a H+

•Conjugate Base: Substances formed in a

Acids, Bases, and Their Conjugates

• NH3+ H2O -- NH4++ OH-

• HCl + H2O --->

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Acids, Bases, and Their Conjugates

• CO3-2+ H2O ---> HCO3- + OH-

• Ca(OH)2 + 2HNO3--> Ca(NO3)2 + 2HOH

Identifying monoprotic, diprotic, andtriprotic:

monoprotic:

HCl H++ Cl- diprotic:

H2SO4 H++ HSO4-1

HSO4-1 H++ SO4-2

triprotic:

H3PO4 H++ H2PO4-1

H2PO4-1 H++ HPO4-2

HPO4-2 H++ PO4-3

Strengths of Acids and Bases

• Strong acids and bases will completely dissociate ex. HCl --> H++ Cl-

• The six strong acids - HCl, HBr,

• HI, H2SO4, HNO3, HClO4

• All others are weak.

• Strong Bases: Groups I

• and II with OH-except Be

Strengths of Acids and Bases

•Weak acids and bases slightly dissociate

ex. HClO <--> ClO-+ H+

Strengths of Acids and Bases

•Strong Acids: HCl, HI, HBr, H2SO4, HNO3, HClO4

•Strong Bases: Groups I and II with OH- except Be

Electrolytes and Non-Electrolytes

•Strong Electrolytes:Strong Electrolytes:Strong Electrolytes:Strong Electrolytes:

- Compounds that conduct electricity in aqueous solution

- Substances that completely dissociate - Strong acids and bases

- Soluble salts

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Electrolytes and Non- Electrolytes

•Weak Electrolytes:Weak Electrolytes:Weak Electrolytes:Weak Electrolytes:

- Slight electron conductivity - Slight dissociation in aqueous - Weak acids and bases

- Insoluble salts if in molten state

Electrolytes and Non- Electrolytes

•NonElectrolytes:NonElectrolytes:NonElectrolytes:NonElectrolytes:

- Don’t conduct electricity - No ions to carry current - Organic, molecular

Examples of Electrolytes and Nonelectrolytes:

• H2S03

• weak acid/weak elect.

• CsOH

• strong base/strong elect.

• HCl04

• strong acid/strong elect.

• C6H1206

• nonelectrolyte- covalent, molecular, organic b/c carbon

Examples of Electrolytes and Nonelectrolytes:

• Al(OH)3

• weak base/weak electrolyte

• HF

• weak acid/weak electrolyte

• CCl4

• nonelectrolyte- molecular compound

• NaN03

• soluble salt/strong electrolyte

• S03

• acid anhydride/weak electrolyte

Neutralization

•Acid + Base > Salt + H2O

•Neutralization is found using titration

•Titration: Analytical method used to determine the concentration of acids, bases in a neutralization reaction.

Neutralization Reactions:

General Equation:

• Acid+ Base Salt+ Water

• HCl+ NaOH NaCl+ HOH Acid Base Salt Water

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Neutralization Reactions:

Titration:Analytical method used to determine the concentration of acids and bases in a neutralization reaction.

1. Measured volume of an acid or base with unknown

concentration. Put in Erlenmeyer.

2. Add a few drops of indicator to the Ernlenmeyer.

3. A measured volume of titrant is delivered into the flask through a buret (base or acid)

4. Concentration of the titrant is known –Standard Solution.

5. Neutralization occurs when indicator is revealed  End Point

6. Equivalence Point MOL ACID = MOL BASE

Titration Curve

Neutralization practice problems:

1. What volume of calcium hydroxide in a 3.0 M solution is needed to neutralize 45.0 mL of 2.6 M perchloric acid?

Neutralization practice problems:

2. Determine the [Ba(OH)2] solution if 300.0 mL was titrated to neutrality with 220.5 mL of 6.0 M solution of phosphoric acid?

Neutralization practice problems:

1. What volume of calcium hydroxide in a 3.0 M solution is needed to neutralize 45.0 mL of 2.6 M perchloric acid?

G: 45 mL 2.6 M HCl04

3.0 M Ca(OH)2

U: ? vol Ca(OH)2

Ca(OH)2+ HCl04 2 HOH + Ca(Cl04)2 0.45 L HCl04x 2.6 mol HCl04x 1 mol Ca(OH)2x 1 L Ca(OH)2

1 L Ca(OH)2 2 mol HCl04 3 mol Ca(OH)2

vol mol mol volM CR M

2. Determine the [Ba(OH)2] solution if 300.0 mL was titrated to neutrality with 220.5 mL of 6.0 M solution of phosphoric acid

G: 220.5 mL 6.0 M H3P04

300.0 mL Ba(OH)2

U: ? M Ba(OH)2

3Ba(OH)2+ 2H3P04 Ba3(P04)2+ 6HOH 0.2205 L H3P04x 6.0 mol H3P04x 3 mol Ba(OH)2

1 L H3P04 2 mol H3P04

= 1.985 mol Ba(OH)2

vol mol molM CR

Figure

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