CHEMISTRY CHAPTER 14 NOTES Acids, Bases, and pH

14.1 ACIDS AND BASES

 

A. ACIDS HAVE A SOUR TASTE, TURN LITMUS RED, AND REACT WITH ACTIVE METALS, CARBONATES, AND BASES.  They are electrolytes.

B. ACIDS IONIZE BY LOSING HYDROGEN IONS TO WATER MOLECULES TO FORM HYDRONIUM IONS, H3O+

C. BASES FORM HYDROXIDE IONS, OH-, WHEN DISSOLVED IN WATER.  IONIC HYDROXIDES ARE BASES BECAUSE THEIR IONS DISSOCIATE.  COVALENT BASES IONIZE BY HYDROGEN TRANSFER FROM WATER MOLECULES TO THE BASE.

 

D. BASES HAVE A BITTER TASTE, A SLIPPERY FEEL, TURN LITMUS BLUE, AND REACT WITH ACIDS.

 

E. ACIDIC ANHYDRIDES ARE NONMETALLIC OXIDES THAT REACT WITH WATER TO FORM ACIDS.

       a). example CO2 SO2, NO2 and rain = H2CO3 carbonic acid

 

F. BASIC ANHYDRIDES ARE METALLIC OXIDES THAT REACT WITH WATER TO FORM BASES.

       a) lime (CaO) added to soil makes soil better for some plants.    CaO  + H2O à Ca(OH)2

              Ca(OH)2 à Ca+   + 2OH-

       b) soap making used anhydrides

              lye + fat = soap

 

G. WATER PLAYS A CENTRAL ROLE IN THE CHEMISTRY OF ACIDS AND BASES.


 

H. NAMING ACIDS AND SALTS

1. Water solutions of binary hydrides form acids. The stem derived from the hydride is given a prefix hydro- and a suffix -ic and is followed by the word acid.

a) The binary hydride HCl is called hydrogen chloride as a gas, but as an aqueous solution it is called hydrochloric acid.

2. Many common acids contain only oxygen, hydrogen, and a nonmetallic ion or a polyatomic ion. Such acids are called oxyacids. The suffixes -ous and –ic indicate the oxidation state of the atom bound to the oxygen and hydrogen. The -ous suffix indicates a lower oxidation state. Table 14-2 lists common acids and anions.

3. In a neutralization reaction an acid reacts with a base to form a salt and H2O. (Many bases can easily be recognized because they are composed of a metallic ion combined with the hydroxide ion. Others, like ammonia, are more difficult to recognize.) The reaction goes to completion since a molecular compound (water) is formed. The water is only slightly ionized. For practical purposes, the water does not react again.

4. The other compound formed is called a salt. Salts are crystalline solids. A salt contains the positive ion of a base and the negative ion of an acid. In addition to common salts such as NaCl and Na2SO4, another group of salts, termed acid salts, contain hydrogen, NaHSO4, sodium hydrogen sulfate; K2HPO4, potassium monohydrogen phosphate; KH2PO4, potassium dihydrogen phosphate. Salts may be soluble or insoluble in water. The common solubility rules are indicated in Table D.8 in Appendix D page 851.

 

 

PROBLEMS

1. Name the following acids.

a. HCl

b. HNO3

c. H2SO4

d. H3PO4

e. HClO3

f. CH3COOH

g. HNO2

h. HClO

i. H2SO3

j. H2CO3

k. HClO2

l. HClO4

2. Name the following salts. Include the name of the acid from which the salt is obtained.

a. NaClO3

b. Fe(ClO4)2

c. NH4BrO3

d. Mg(IO3)2

e. MnI2

f. Ba(NO3)2

g. PbCl2

h. Hg(BrO3)2

i. ZnSO4

j. Ca(ClO)2

3. Write formulas for each salt and write the formula of the acid from which the salt can be obtained.

a. ammonium sulfate

b. barium hypochlorite

c. lithium chlorate

d. cobalt(II) sulfite

e. mercury(I) bromate

f. chromium(III) nitrate

g. magnesium chloride

h. potassium perchlorate

SECTION REVIEW

1. Name the following acids.

a. HBr

b. HNO2

c. H2SO4

d. H2S

e. H3PO3

f. HClO3

g. HI

h. CH3COOH

i. H3AsO4

j. HIO3

k. H2SiO3

l. H2CO3

2. Write formulas for the following. Identify each as acid, base, or salt.

a. magnesium hydroxide

b. hydrochloric acid

c. zinc nitrate

d. sulfurous acid

e. sodium hypochlorite

f. potassium hydroxide

 

14.2 STRENGTHS OF ACIDS AND BASES

Litmus Tests

A. STRENGTHS OF ACIDS AND BASES

THE STRUCTURE OF ACIDS AND COVALENT BASES DETERMINES THEIR STRENGTH.

 

1. STRONG ACIDS AND BASES COMPLETELY DISSOCIATE OR IONIZE

       a) A strong acid such as hydrochloric acid exists in solution as ions.

b) The concentration of H3O+ ions determines the strength of an acid. When a weak acid dissolves in water, an equilibrium is established between the molecular form and the ionic form of the substance.

c) The reverse reaction is favored. As a result, there is a small concentration of ions. The amount of ionization is directly related to acid strength. Strong bases, such as sodium hydroxide, also dissolve in water to form ions.

2. MOST ACIDS AND BASES ARE WEAK.  WEAK ACIDS AND BASES FORM FEW IONS.

a) When NH3(g), a weak base, dissolves in water, few ions are produced.

b) About 99% of the NH3(g) remains in the molecular form. As with acids, the amount of ionization is directly related to base strength.

3. THE pH SCALE IS A CONVENIENT WAY TO COMPARE THE ACIDITY AND BASICITY OF SOLUTIONS.

a) ACID-BASE INDICATORS ARE LISTED ON PAGE 852 TABLE D.10

The table shows the chemical equations of some typical reactions involving acidic compounds and basic compounds. Study the equations and answer the questions that follow.

 

1. For each of the reactions described in the table, fill in the type of reactants involved and the type of products yielded. The first four lines are completed for you.

2. Examine the completed table and determine how many ways the listed reactions might be classified based on the products yielded. List the categories you identify.

3. How many ways might the reactions be classified based on the reactant involved? List the categories you identify.

4. What three general combinations of reactants yield a salt + water product?

5. Complete and balance each of the following equations. Then classify each equation based on the reactants involved.