Section 2.4—Defining, Naming & Writing Acids & Bases

We need to know what acids behave when talking about ant-acids!

Acids

Acids – Arrhenius Definition

Produce Hydronium ion (H3O+1) in water

Hydronium ion is water + a hydrogen cation

H

OH

water

H+1

H

OH

H +1

By this definition, if an acid is to give a H+1 to water, then all acids will have hydrogen as the cation (first element written).

How do Acids produce Hydronium?

H

OH

H -

water acid

Hydrogen cation with some anion

How do Acids produce Hydronium?

H

OH

H -+1

How do Acids produce Hydronium?

H

OH

H+1 -

Hydronium ion Anion

Naming Acids

These compounds have:Start with “H” (more than 1 “H” is OK, too).Do not contain oxygen

To name these compounds:Use “hydro____ic acid”Fill in the blank with the anion’s name without

the last syllable

Naming non-oxygen Acids

Example #1

HBr

Example #1

HBr

Hydrogen cation

Bromine

It’s an acid

No oxygenUse “hydro___ic”

Hydrobromic acid

These compounds have:Start with “H” (more than 1 “H” is OK, too).Do contain oxygen

To name these compounds:Use “___ic acids” for “-ate” anionsUse “___ous acids” for “-ite” anions

Naming Oxygen Acids

Do not use “hydro” with these…the word “acid” is how you know it begins with hydrogen, not “hydro-”

Example #2

H2SO3

Example #2

Hydrogen cation

Sulfite ion

It’s an acid

“-ite” ionUse “___ous” acid

H2SO3

Sulfurous acid

Example #3

H2SO4

Example #3

Hydrogen cation

Sulfate ion

It’s an acid

“-ate” ionUse “___ic”

H2SO4

Sulfuric acid

Let’s Practice

Example:Write the name for the following

compounds

HCl

HNO3

H2S

H3PO3

Let’s Practice

Hydrochloric acid

Nitric acid

Hydrosulfuric acid

Phosphorous acid

Example:Write the name for the following

compounds

HCl

HNO3

H2S

H3PO3

Writing Acid Formulas

To write these formulas:The cation is H+1

Write the anion and chargeBalance the charges by adding the appropriate

subscript to the hydrogen cation

“Hydro-” acids

Example #4

Hydrofluoric acid

Example #4

Hydrofluoric acid

Hydrogen cation

Does not contain oxygen

H+1

F-1

Example #4

Hydrofluoric acid

Hydrogen cation

Does not contain oxygen

H+1

F-1

HF

H+1F-1

+1 + -1 = 0

The compound is neutral.Subscripts are not needed

To write these formulas:The cation is H+1

If it is an “-ic” acid, the anion is the “-ate” polyatomic ion

If it is an “-ous” acid, the anion is the “-ite” polyatomic ion

Add subscript to the hydrogen cation to balance charges

NON “Hydro-” acids

Example #5

Carbonic acid

Example #5

Carbonic acid

Hydrogen cation

From the “___ate” anion

H+1

CO3-2

Example #5

Carbonic acid

Hydrogen cation

From the “___ate” anion

H+1

CO3-2

H2CO3

H+CO32-

+1 + -2 = -1

H+H+CO32-

+1 + 1 + -2 = 0

Example #6

Nitrous acid

Example #6

Nitrous acid

Hydrogen cation

From the “___ite” anion

H+1

NO3-1

Example #6

Nitrous acid

Hydrogen cation

From the “___ite” anion

H+1

NO3-1

HNO2

H+NO2-

+1 + -1 = 0

Let’s Practice

Example:Write the

formula for the following acids

Phosphoric acid

Hydroiodic acid

Carbonous acid

Perchloric acid

Phosphoric acid

Hydroiodic acid

Carbonous acid

Perchloric acid

Let’s Practice

H3PO4

HI

H2CO2

HClO4

Example:Write the

formula for the following acids

Bases

Bases – Arrhenius Definition

Bases produce the hydroxide ion in water

HO-1

Hydroxide Ion

Naming & Writing Bases

Most bases are just ionic compounds with “hydroxide” as their anion

The most common exception to this is ammoniaNH3 (ammonia) is a base even though it doesn’t

contain “-OH” as the anion

Naming Bases

Example #7

NaOH

Example #7

NaOH

Sodium

Hydroxide

Sodium Hydroxide

Let’s Practice

Example:Write the formula or

name for each

Ca(OH)2

KOH

Sr(OH)2

Copper (II) hydroxide

Magnesium hydroxide

Let’s Practice

Calcium hydroxide

Potassium hydroxide

Strontium hydroxide

Cu(OH)2

Mg(OH)2

Example:Write the formula or

name for each

Ca(OH)2

KOH

Sr(OH)2

Copper (II) hydroxide

Magnesium hydroxide