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Grade: Senior
Subject: Science

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#107. Acids, Bases and Salt - Background and Naming

Science, level: Senior
Posted by Michael H. Edmondson (medmond@hotmail.com).
Hardaway High School, USA
Materials Required: Pencil, paper
Activity Time: 2-3 class periods
Concepts Taught: Characteristics and naming of acids, bases and salts

OUTLINE OF INFORMATION
ACIDS, BASES, SALTS

ACIDS

1. Form hydronium ions in water
2. Never "taste test" an acid
3. Always add acid to water and never the reverse
4. Important acids
a. Sulfuric acid
1. H2SO4
2. 98% by weight in concentrated form (per liter)
3. density is 1.84 g/ml
4. dilute is 1 part concentrated to 6 parts water
b. Nitric acid
1. HNO3
2. concentrated form is 70% by weight (per liter)
3. density is 1.42 g/ml
4. dilute is one part concentrate to 5 parts water
c. Hydrochloric acid
1. HCl
2. concentrated is 36% by weight (per liter)
3. dilute is one part HCl (concentrated) per 4 parts water
5. Bronsted definition: proton donor

Properties of Acids:

1. Donate protons to bases
2. Contain ionizable hydrogen in covalent bond with nonmetal or polyatomic ion
3. Strength depends on degree of ionization
4. Sour taste
5. Affect indicators
6. Neutralize hydroxides
7. React with metals, releasing hydrogen
8. React with metal oxides
9. React with carbonates

Acidic anhydrides are nonmetallic oxides

BASES

A. Defined
Proton acceptors (Bronsted)
B. Properties
1. Hydroxides of active metals supply OH- in water solution
2. Strength of bases depends upon the hydroxide ion concentration in solution
3. Have bitter taste
4. Feel slippery
5. Affect indicators
6. Neutralize acids, forming water as one product
7. React with nonmetal oxides
8. All metallic hydroxides (except those of active metals) are pretty much insoluble in water. They are weakly acidic in the presence of strong bases. That is, they are amphoteric, which means that they may act like an acid or a base.
9. Fe(OH)3 is not amphoteric

C. Basic anhydrides

metallic oxide + water ----> base

CONJUGATES

Conjugate base is what remains when an acid gives up its proton.
Conjugate acid is what remains when a base takes on a proton.

From the Bronsted definition:

(1) The stronger an acid the weaker its conjugate base; the stronger a base the weaker is its conjugate acid

(2) Protolysis (splitting off of a proton) favors the weaker acid and weaker base. In other words, the weaker the acid the less it dissociates/ionizes.

Examples:

HCl + H2O <----> H3O+ + Cl-
acid "base" conjugate conjugate
acid base

The above reaction goes mostly to the right; high ionization (from statement (1) above).

HC2H3O2 + H2O <----> H3O+ + C2H3O2
acid "base" conjugate conjugate
acid base
(vinegar, acetic
acid, ethanoic
acid)

The above reaction goes mostly to the left. There is low ionization of the acetic acid. There are mostly molecules (and therefore few ions) in solution.

SALTS

Compound formed of positive ions of aqueous bases and negative ions of aqueous acids. The solubility of salts in water varies.

Salt-Producing Reactions:

1. Direct element union
2. Metal reacting with an acid
3. Reaction of nonmetallic oxide with aqueous acid
4. Reaction of nonmetallic oxide with aqueous base
5. Acid-base neutralization
6. Ionic reaction
7. Reaction of acid with a carbonate
9. Reaction of a metallic oxide with a nonmetallic oxide

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Naming Acids:

A. Binary

"hydro" + nonmetal stem + "ic" "acid"

B. Oxyacids
Contain oxygen, hydrogen, and a third element
You have a base acid (names for all others of the series are based upon this acid)

Acid of the same series with one more oxygen than the base acid is
"per" + stem + "ic" "acid"

Base acid

stem + "ic" "acid"

One less oxygen than the base acid

stem + "ous" "acid"

Two less oxygens than the base acid

"hypo" + stem + "ous" "acid"

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Naming Bases:
metal name + "hydroxide"

Example: NaOH sodium hydroxide

If the metal has a variable oxidation number, be sure to include that information.

Example: CuOH copper (I) hydroxide
Cu(OH)2 copper (II) hydroxide

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Naming of Salts:

NOTICE THAT THESE RULES FOR NAMING SALTS ARE THE SAME AS YOU ALREADY LEARNED EARLIER IN THE YEAR.

Stock system from IUPAC used for this.

1. Positive named first. (cation)
2. If variable oxidation possible, use Roman numerals in parentheses to indicate the oxidation state of the cation.
3. If 2 positives (2 metals) present, the most electropositive is named first.
4. Anions (negative ions) are named from the acid name from which they originate:
If the ending was "ic" in the acid, it becomes "ate" in the salt.
If the ending was "ous" in the acid, it becomes "ite" in the salt. The prefix (if there was one present on the acid) would remain and be unchanged on the salt anion.
5. A binary salt has
stem + "ide"

as the second word in the name. The first word is the positive (cation).

Examples:

Binary
LiF: lithium fluoride

Binary (variable oxidation number)

FeBr2 iron (II) bromide

FeBr3 iron (III) bromide

A salt formed from each of the following acids and bases reacting:

(1) HClO4 + NaOH ----> NaClO4 + H2O
perchloric sodium sodium water
acid hydroxide perchlorate

(2) HClO3 + NaOH ----> NaClO3 + H2O
chloric sodium sodium water
acid hydroxide chlorate

(3) HClO2 + NaOH ----> NaClO2 + H2O
chlorous sodium sodium water
acid hydroxide chlorite

(4) HClO + NaOH ----> NaClO + H2O
hypochlorous sodium sodium water
acid hydroxide hypochlorite

If the reaction involves an oxyacid (or any type acid, for that matter) reacting with a variable oxidation number base, be sure to include that information.

Example:

H3PO4 + Cu(OH)2 ----> Cu3(PO4)2
phosphoric copper (II) copper (II) phosphate
acid hydroxide

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