Chapter 19: Acids/Bases
Properties of an Acid:
1. Taste sour or tart
2. Electrolytic in solution (will conduct
electricity when dissociated):
a. strong acid = strong electrolyte
b. weak acid = weak electrolyte
3. React w/ metal produces H2
4. Reacts w/ OH for neutralization
Properties of Bases:
1. Feels slippery like soaps
2. Taste bitter
3. Electrolytes in solution
a. strong bases = strong electrolyte
b. weak bases = weak electrolyte
4. Reacts w/ acids to neutralize
Types of Acids/Bases
Lewis Acid: Accepts an electron pair.
Lewis Base: Donates an electron pair.
Bronsted/Lowery Acid: proton donor (H+)
Bronsted/Lowery Base: proton acceptor (H+)
*Arrhenius Acids: contain hydrogens and
produces H+
*Arrhenius Base: produces hydroxide ions
(OH-)
Naming Acids
1. Binary Acids: formed by the bonding of a
hydrogen to a simple anion (Cl-, F-, S2-)
hydro - root - ic
HCl - hydro chlor ic
(hydrochloric acid)
HBr - hydro brom ic
(hydrobromic acid)
H2S - hydro sulfur ic
(hydrosulfuric acid)
2. Ternary Acids: formed by the bonding of
H+ to a polyatomic ion
-ate -ic, ite -ous (NEVER A HYDRO-)
HNO2 : NO2 is nitrite, so the root is nitr- ending in -ous.
Nitrous acid
H3PO4 : PO is phosphate, so the root is phosphor- ending in -ic.
Phosphoric acid
Use your reference page for the anion roots!
4
Practice Problems
Name or write the formula for the following
1. Acetic acid
2. Cyanic acid
3. Nitric acid
4. Hydroiodic acid
5. Boric acid
6. Sulfuric acid
7. HBr
8. H2SO4
9. H2CO3
10. HF
Naming Bases
Bases are compounds the produce hydroxide
ions (OH-) when dissolved in water.
Element name then hydroxide
NaOH :
Sodium hydroxide
Fe(OH)3 :
Iron (III) hydroxide
Bases
CuOH :
Copper (I) hydroxide
Cu(OH)2 :
Copper (II) hydroxide
Strength of Acids and Bases
The strength of an acid or base is defined by
the dissociation of the acid or base.
Strong Acids and Base = 100% dissociation
Weaker Acids and Bases = less than 100%
*there are therefore degrees of weak
defined by a ratio of dissociation, Ka &
Kb.
Concentration defines strength.
How is concentration expressed?
Molarity
Molarity: expression of concentration.
Molarity = # of moles of solute
# of liters of solution
M = moles/liter
1. What is the molarity of 3.65 g of HCl
dissolved to a volume of 2 L?
*Convert mass to moles
*Calculate the molarity
Molarity: Sample Problems
1. What is the molarity of a solution of
sulfuric acid when 49.04 g of sulfuric acid is
dissolved in 250 ml of water?
2. What mass of barium hydroxide is needed
to make 2.5 L of a 0.06 molar solution?
3. What is the molarity of a solution made
from 9.94 g of CoSO4 and 250 ml of water?
4. How many grams of AgF are needed to
make 500-ml of a 1.5 M solution?
Auto-ionization/Self-ionization
Refers to the breakdown of H2O to ions.
H2O  H+ + OHChcts:
1. reversible
2. neutral state = 50/50 ratio
3. Kw ionization product constant of
water.
Other than Water
If the concentration of H+ is greater than
OH-, then the solution is acidic.
[H+] > [OH-]  acidic solution
If the concentration of H+ is less than OH-,
then the solution is basic
[H+] < [OH-]  basic solution
The pH Scale
A. pH Scale: a scale relative to the [H+] to
[OH-].
1. Scale:
14 ------------------- 7 ---------------------- 0
Basic
Neutral
Acidic
2. pH = -log [H+]
3. pOH = -log [OH-]
pH Problems
1. [H+] : 6.5 x 10-10 = pH of ___________
2. [H+] : 6.8 x 10-10 = [OH-] ___________
3. pH = 4.697 is a [H+] = _______________
4. What is the pOH of problem #3. _______
5. pOH = 8.992, what is the pH : _________
6. [H+] is 3.7 x 10-6, what is the pH: ______
7. What is the [OH-] in #6
4. Chstc:
a. pH + pOH = 14
b. Kw = [H+] x [OH-] (add exponents)
c. [H+] = inv log or antilog -pH
d. [OH-] = inv log or antilog -pOH
5. Indicators: substances that change color
in the present of an acid or base.
Acid/Base Strengths
A. Keq: Equilibrium rate constant for a
reaction. Describes a point of equilibrium
for a reaction.
1. Depends on solubility. See table.
a. Greater solubility = stronger solution
b. Keq = [product(s)] / [reactant(s)]
HCl + H2O  H3O+ + Cl-
Ka : Acid Dissociation Constant
Ka = [Product (s)] / [Reactant(s)]
4HCl + O2  2Cl2 + 2H2O
1. Chcts:
a. concentrations raise to the power of the
coefficient in a balanced equation.
b. Smaller the Ka the weaker the acid
c. Large Ka means large dissociation.
Kb : Base Dissociation Constant
Kb = [Product(s)] / [Reactant(s) ]
KOH  K+ + OH1. Chstc:
a. Smaller Kb = weaker bases
b. Large Kb means large dissociation.
Table 19.5 and 19.6 pages 557 and 558.
Ka and Kb Sampler
Calculate the Ka from pH:
1. Write the balanced equation.
2. Write the Ka or Kb expression.
3. Use the given pH to find [H+].
4. Distribute the [ ] & subtract from the
initial [ ].
The pH of a 0.2 M HC2H3O2 is 2.72. What
is the Ka for acetic acid?
Practice Problems
1. Given a 0.1 M solution of sulfurous acid
with a pH of 1.48, calculate the Ka.
2. A 0.2 M solution of benzoic acid,
C6H5COOH has a pH of 2.45. What is the
Ka ?
3. A basic solution with a pH of 12.5 has a
concentration of 0.25 M BOH. What is
the Kb?
Calculating pH from Ka or Kb
1.
2.
3.
4.
Write a balanced equation.
Write the Ka or Kb expression.
Use the equation diagram to define ‘x’.
Using the given Ka (Kb) , insert ‘x’ for
[H+] and [A-].
5. Eliminate ‘x’ in the denominator.
6. Solve for ‘x’
7. Calculate pH or pOH
Calculate pH from Ka/Kb
1. A given 0.15 M solution of nitrous acid,
HNO2, has a Ka = 3.45 x 10-5. What is
the pH?
2. A solution of 0.2 M, CsOH , has a
Kb = 1.25 x 10-8. What is the pH ?
3. A solution is prepared by adding 56.3 g
of HCl and 62.1 g of NaOH to enough
water to make 250 ml. Determine the pH
of the solution?
Titration
Titration is a process by which a solution of
known concentration is used to determine
the concentration of an unknown solution.
Indicators: Chemicals that are effected by
pH and used to determine the equivalent
point.
Equivalent Point: point of neutralization.
The pH at this point depends on the
strength of the acids/base involved.
Calculating
Process to determine the [ ] of an unknown
solution from a known solution.
Setup ?
pH meter
Indicators: changes color @ end-point
End-point: indicates pH range via indicator
Equivalent point (ovhd) mole H+= moles OHBuffer :reduce change in pH. Hold pH steady
Buffer Capacity: amount of acid/base that
can be absorbed before change in pH
increase [ ] = increase in capacity
Buffers contain common ions or weak acids
and their conjugate base.
What is the buffer for the reaction:
HCN  H+ + CNAns: any salt that contained CN- that will
reverse the reaction thereby reducing H+
Calculations with titration
Find the [ ] of an unknown by titration
It takes 26.4 ml of 0.25 M HBr solution to
neutralize 30 ml of CsOH. Find [ ]
1. Write a balanced equation
2. Convert
ml  L  given [ ]  mole ratio  [?]
ans: 0.22 M CsOH
What is the [ ] of nitric acid if 43.33 ml of a
0.1 M KOH is neutralize 20 ml of HNO3 ?
1. Balance the equation.
2. Convert
ml  L  given [ ]  mole ratio  [ ]
3. Use [ ] to calculate pH.
Textbook: p621 #32-33 ; p631 #72-80
p 632 #93-96
Sampler
1. What is the concentration of a
household ammonia solution if 4909
ml 0.59 M HCl is required to neutralize
25 ml solution?
2. In a titration, 33.21 ml 0.3020 M
rubifium hydroxide solution is required
to exactly neutralize 20 ml of HF acid
solution. What is the molarity of HF ?