Drop the Base

Anger is an acid that can do more harm to the vessel in which it is stored than to anything on which it is

poured.- Mark Twain

What we already know…

Acids are solutions with hydronium ions in solution.

Bases are solutions with hydroxide ions in solution.

Acids and Bases can be classified as Strong if they ionize completely

Acids and Bases can be classified as Weak if they do NOT ionize completely

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What’s an Acid?Arrhenius – a substance that increase the number of [H+] ions when mixed with water

Brǿwnsted-Lowry – substances that donate protons (H+)

Lewis – a substance that can accept electrons

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Common Acids

Acetic AcidCarbonic AcidCitric AcidHydrochloric AcidPhosphoric AcidSulfuric Acid

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What’s a Base?

Arrhenius Base – a substance that increase the number of [OH] ions when mixed with water

Brǿwnsted-Lowry Base – substances that accepts protons

Lewis Base – a substance that can donates electrons

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Common Bases

AcetoneAmmoniaCalcium hydroxideLithium hydroxidePyridineSodium hydroxide

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All thumbs are fingers but not all fingers are thumbs…

All Arrhenius acids are Brǿwnsted-Lowry acids, and all BL acids are Lewis acids

Not all Lewis acids are Brǿwnsted-Lowry or Arrhenius acids

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Example

Draw a mechanism showing how HCl acid meets the definition for each type of acid.

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Strong Acids & Strong Bases (MEMORIZE!)Strong Acids and Bases completely disassociate in water (Arrhenius).

Name Chemical Formula

Hydroiodic acid

HI

Hydrobromic acid

HBr

Perchloric acid HClO4

Hydrochloric acid

HCl

Sulfuric acid H2SO4

Nitric acid HNO3

Name Chemical Formula

Sodium hydroxide NaOH

Potassium hydroxide KOH

lithium hydroxide LiOH

Rubidium hydroxide RbOH

Cessium hydroxide CsOH

Calcium hydroxide Ca(OH)2

barium hydroxide Ba(OH)2

strontium hydroxide Sr(OH)2

Naming Acids

Similar to polyatomic ions but one BIG change

Anions Name Change -ate -ic-ous -ite-ide hyrdo-____-ic

Naming Bases

Bases follow the same rules as polyatomic ions.

Name the cation followed by the anion (hydroxide)

If the cation is a transition metal indicate the oxidation number

Conjugate Acids and Bases

What about water?

Measuring Acid Strength

pH = -log [H+]

Name Variable Definition Units Measured by

Acid Strength

pH Logarithmic measurement of the ability of a substance to form hydronium ions in solution

NONE pH probe, litmus paper

Hydrogen Ion

Concentration

[H+] The concentration of hydronium ions present in solution

M Calculated or Counted (not

feasible)

Measuring Base Strength

pOH = -log [OH-]

Name Variable Definition Units Measured by

Base Strength

pOH Logarithmic measurement of the ability of a substance to form hydroxide ions in solution

NONE pH probe, litmus paper

Hydroxide Concentrati

on

[OH-] The concentration of hydroxide ions present in solution

M Calculated or Counted (not

feasible)

pH Scale

Measuring Acid Strength

pH probes

Litmus Paper

Water Disassociation

Water will disassociate by itself in a very small amount

H2O [H+][OH-]

Kw = [H+][OH-] = 1.0 X 10-14

[H2O]

Relating pH to pOH

pH + pOH = 14

Name Variable Definition Units Measured by

Base Strength

pOH Logarithmic measurement of the ability of a substance to form hydroxide ions in solution

NONE pH probe, litmus paper

Acid Strength

pH Logarithmic measurement of the ability of a substance to form hydronium ions in solution

NONE pH probe, litmus paper

Example B-1

H2SO4 is a strong acid. What is the name, pH and pOH of a solution of a 15.8 M solution?

Example B-2

Write an equation for the ionization of water. What is the pH and pOH of water?

Example B-3

A has a pH of 3.6. How many hydronium ions are present in a 25 mL sample of solution?

Example B-4

What is the pH of a solution containing 1.4 X 10-

10 M [H+]? Classify the substance as an acid, neutral or base.

Acid Disassociation

Acids and Bases disassociate very similar to ions

HA [H+][A-]

We can write a disassociation expression as:

Strong Acids

Strong Acids disassociate COMPLETELY (or close to it)

The expression is meaningless/infinity

And this simplifies to

Initial Concentration of S.A. = Final Concentration of [H+]

Weak Acids

Weak Acids partially disassociate

The expression is crucial to determining [H+] Concentration

Initial Concentration of S.A. = Final Concentration of [H+]

Example D-1

The acid disassociation constant for acetic acid is 1.58 X 10-5. What is the pH of a solution of 0.15 M acetic acid? How does this compare to the pH of 0.15 M hydrochloric acid?

Base Disassociation

Bases disassociate very similar to ions

BOH [B+][OH-]

We can write a disassociation expression as:

Strong Bases

Strong bases disassociate COMPLETELY (or close to it)

The expression is meaningless/infinity

And this simplifies to

Initial Concentration of S.B. = Final Concentration of [OH-]

Weak Bases

Weak Bases partially disassociate

The expression is crucial to determining [OH-] Concentration

Initial Concentration of S.B. = Final Concentration of [OH-]

Example E-1

The disassociation constant for pyridine is 1.8 X 10-9. What is the pH of a solution of 0.15 M pyridine?

Percent Ionization

Percent Ionization = Concentration Ionized X 100 Original Concentration

Example D-1

Calculate the percent ionization for a solution of 0.01 M benzoic acid where Ka = 6.31 X 10-5.