18.1 Introduction to Acids and Bases
1. Name the following compounds as acids:
__________________________________________________________a.
H2SO4
__________________________________________________________d.
HClO4
__________________________________________________________b.
H2SO3
__________________________________________________________e.
HCN
__________________________________________________________c.
H2S
2. Which (if any) of the acids mentioned in item 1 are binary acids?
3. Write formulas for the following acids:
___________________________________________________a. nitrous acid
___________________________________________________d. acetic acid
__________________________________________________b. hydrobromic acid
__________________________________________________e. hypochlorous acid
___________________________________________________c. phosphoric acid
4.
Calcium selenate has the formula CaSeO4.
a.
What is the formula for selenic acid?
b.
What is the formula for selenous acid?
5.
Identify the Brønsted-Lowry acid and the Brønsted-Lowry base on the reactant side of each of the following equations for reactions that
occur in aqueous solution. Explain your answers.
a. H 2 O(l )  HNO 3 (aq )  H 3 O  (aq )  NO 3 (aq )
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
b. HF(aq) + HS-(aq)  H2S(aq) + F-(aq)
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
Example Problem 1
Identifying Conjugate Acid-Base Pairs
Identify the conjugate acid-base pairs in this reaction.
HClO2(aq) + H2O(l)  H3O+(aq) + ClO2-(aq)
6.Identify the conjugate acid-base pairs in the following reactions.
a. H2SO3(aq) + H2O(l)  HSO3-(aq) + H3O+(aq)
b. HPO42-(aq) + H2O(l)  H2PO4-(aq) + OH-(aq)
c. HSeO3-(aq) + H2O(l)  H3O+(aq) + SeO32-(aq)
7. Write the steps in the complete ionization of the following polyprotic acids.
a. carbonic acid (H2CO3)
b. chromic acid (H2CrO4)
8. Answer the following questions according to the Brønsted-Lowry definitions of acids and bases:
___________________________ a. What is the conjugate base of H2SO3?
___________________________ d. What is the conjugate acid of H2O?
___________________________ b. What is the conjugate base of NH 4 ?
___________________________ e. What is the conjugate acid of HAsO 2  ?
4
___________________________ c. What is the conjugate base of H2O?
9.Consider the reaction described by the following equation:


NH 4 (aq )  CO 32 (aq ) 
 NH 3 (aq )  HCO 3 (aq )
a. If NH 4 is considered acid 1, identify the other three terms as acid 2, base 1, and base 2 to indicate the conjugate acid-base pairs.
_______________________________ CO 32 
_______________________________ HCO 
_______________________________ NH3
3
_______________________________ b. A proton has been transferred from acid 1 to base 2 in the above reaction. True or False?
2
10.Consider the neutralization reaction described by the equation: HCO 3 (aq)  OH  (aq) 
 CO 3 (aq )  H 2 O(l )
a. Label the conjugate acid-base pairs in this system.
b. Is the forward or reverse reaction favored? Explain your answer.
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
18.2 Strengths of Acids and Bases
Strong Acid: _______________________________________
Strong Base: _______________________________________
List the strong acids: ____________________________________________________________________
List the strong bases: ________________________________________________________________________
11. Write ionization equations and acid ionization constant expressions for the following acids.
a. hydrofluoric acid (HF)
b. hypobromous acid (HBrO)
12.Write the ionization equation and the acid ionization constant expression for the second ionization of sulfurous acid (H2SO3) in water.
Practice Problems
13.Write ionization equations and base ionization constant expressions for the following bases.
a. butylamine (C4H9NH2)
b. phosphate ion (PO43-)
c. hydrogen carbonate ion (HCO3-)
14.Write net ionic equations that represent the following reactions:
a. the ionization of HClO3 in water
____________________________________________________________________________________________________________________
b. NH3 functioning as an Arrhenius base
____________________________________________________________________________________________________________________
15. a. Explain how strong acid solutions carry an electric current.
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
b. Will a strong acid or a weak acid conduct electricity better, assuming all other factors remain constant? Explain why one is a better
conductor.
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
16. a. Write the two equations that show the two-stage ionization of sulfurous acid in water.
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
b. Which stage of ionization usually produces more ions? Explain your answer.
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
17. a. Write the equation for the first ionization of H2CO3 in aqueous solution. Assume that water serves as the reactant that attaches to the
hydrogen ion released from the H2CO3. Which of the reactants is the Brønsted-Lowry acid, and which is the Brønsted-Lowry base?
Explain your answer.
_________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________
b. Write the equation for the second ionization, that of the ion that was formed by the H 2CO3 in the reaction you described above. Again,
assume that water serves as the reactant that attaches to the hydrogen ion released. Which of the reactants is the Brønsted-Lowry
acid, and which is the Brønsted-Lowry base? Explain your answer.
_________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________
18. Write the formula for the salt formed in each of the following neutralization reactions, and identify if the salt is acidic, basic, or neutral:
___________________________________ a. potassium hydroxide combined with phosphoric acid
___________________________________ b. calcium hydroxide combined with nitrous acid
___________________________________ c. hydrobromic acid combined with barium hydroxide
___________________________________ d. lithium hydroxide combined with sulfuric acid
19. Consider the following unbalanced equation for a neutralization reaction:
H2SO4(aq) + NaOH(aq)  Na2SO4(aq) + H2O(l)
a. Balance the equation.
____________________________________________________________________________________________________________________
___________________________________ b. In this system there are two spectator ions. Identify them.
___________________________________ c. For the reaction to completely consume all reactants, what should be the mole ratio of acid to base?
18.3 Hydrogen Ions and pH
Example Problem 2
Using Kw to Calculate [H+] and [OH-]
At 298 K, the OH- ion concentration of an aqueous solution is
1.0x10-11M. Find the H+ ion concentration in the solution and determine whether the solution is acidic, basic, or neutral.
20.Given the concentration of either hydrogen ion or hydroxide ion, calculate the concentration of the other ion at 298 K and state whether the
solution is acidic, basic, or neutral.
a. [OH-] = 1.0x10-6M
b. [H+] = 1.0x10-7M
c. [H+] = 8.1x10-3M
Example Problem 3
d. [OH-] = 0.061M
Calculating pH and pOH from [H+]
Example Problem 4
If a certain carbonated soft drink has a hydrogen ion
Calculating [H+] and [OH-] from pH
concentration of 7.3x10-4M, what are the pH and pOH of the soft
What are [H+] and [OH-] in an antacid solution with a pH of 9.70?
drink?
Use pH to find [H+].
21.Calculate the pH and pOH of aqueous solutions having the
22.The pH or pOH is given for three solutions. Calculate [H+] and
following ion concentrations.
[OH-] in each solution.
a. [H+] = 1.0x10-14M
a. pH = 2.80
b. [OH-] = 5.6x10-8M
b. pH = 13.19
c. [H+] = 2.7x10-3M
c. pOH = 8.76
23.Calculate the pH of the following strong acid or strong base solutions.
a. 0.015M HCl
c. 2.5x10-4M HNO3
b. 0.65M KOH
d. 4.0x10-3M Ca(OH)2
Example Problem 5
Calculating Ka from pH
The pH of a 0.200M solution of acetic acid (CH3COOH) is 2.72. What is Ka for acetic acid?
24.Calculate Ka for the following acids using the information provided.
a. 0.100M solution of sulfurous acid (H2SO3), pH = 1.48
b. 0.200M solution of benzoic acid (C6H5COOH), pH = 2.45
25.
Calculate the following values
_____________________a.
The [H3O+] is 1 x 10-6 M in a
solution. Calculate the [OH-].
_____________________b.
The [H3O+] is 1 x 10-9 M in a
solution. Calculate the [OH-].
_____________________c.
The [OH-] is 1 x 10-12 M in a
solution. Calculate the [H3O+].
_____________________d.
The [OH-] in part c is reduced by half,
to 0.5 x 10-12 M. Calculate the [H3O+].
_____________________e.
The [H3O+] and [OH-] are _____
(directly, inversely, or not) proportional in any system involving
water.
26.
Calculate the following values
_____________________a.
The pH of a solution is 2.0. Calculate
the pOH.
_____________________b.
The pOH of a solution is 4.73.
Calculate the pH.
_____________________c.
The [H3O+] in a solution is 1 x 10-3
M. Calculate the pH.
_____________________d.
The pOH of a solution is 5.0.
Calculate the [OH-].
_____________________e.
The pH of a solution is 1.0. Calculate
the [OH-].
27.
Calculate the following values.
_____________________a.
The [H3O+] is 2.34 x 10-5 M in a
solution. Calculate the pH.
_____________________b.
The pOH of a solution is 3.5.
Calculate the [OH-].
_____________________c.
The [H3O+] is 4.6 x 10-8 M in a
solution. Calculate the [OH-].
28.
[H3O+] in an aqueous solution = 2.3 x 10-3 M.
_____________________a.
Calculate [OH-] in this solution.
_____________________b.
Calculate the pH of this solution.
_____________________c.
Calculate the pOH of this solution.
_____________________d.
Is the solution acidic, basic, or
neutral? Explain your answer.
29. Consider a dilute solution of 0.025 M Ba(OH)2 in answering
the following questions.
_____________________a.
What is the [OH-] in this solution?
Explain your answer.
_____________________b.
What is the pH of this solution?
30. Vinegar purchased in a store may contain 6 g of CH3COOH per
100 mL of solution.
_____________________a.
What is the molarity of the solute?
b.
The actual [H3O+] in the vinegar solution in part a is 4.2
x 10-3 M. In this solution, has more than 1% or less than 1% of the
acetic acid ionized? Explain your answer.
_____________________________________________
_____________________c.
Is acetic acid strong or weak, based
on the ionization information from part b?
_____________________d.
What is the pH of this vinegar
solution?
Worksheet: Ka Kb Kw Fun!
1. Benzoic acid, HC6H5CO2, is an organic acid whose sodium salt, NaC6H5CO2, has long been used as a safe food additive to
protect beverages and many foods against harmful yeasts and bacteria. The acid is monoprotic. Write the equation for its Ka.
2. The [H+ ] of a 0.10 M solution of cyanic acid (HCNO) is found to be 0.0010 M. Calculate the Ka for cyanic acid. HCNO ↔ H+ +
CNO‐
3. If 1.22 grams of benzoic acid, HC6H5CO2, is dissolved in 1.0 L of water, the [H+ ] is found to be 8.0 x 10‐4 M. Calculate the Ka
for benzoic acid. HC6H5CO2 ↔ H+ + C6H5CO21‐
4. A 0.0050 M solution of butyric acid, HC4H7O2, has a pH =4.0, calculate Ka.
HC4H7O2 ↔ H+ + C4H7O21‐
5. Determine the [OH‐ ] and the [H+ ] of a 0.20 M solution of formic acid. The Ka = 1.8 x 10‐4
HCOOH ↔ H+ + HCOO‐
6. HCN has an initial molarity of 0.50 M, with a Ka value of 3.7 x 10‐8 . Calculate its pH at equilibrium. (Hint: This is an ICE
problem.)
7. Ethylamine (C2H5NH3) is a weak Bonsted‐Lowry base. If it has an initial molarity of 0.024 M and a Kb of 5.6 x 10‐4 ,
calculate its pH at equilibrium. (Hint: This is an ICE Problem.)
8. A chemist adds 0.75 moles of NH3 to enough water to make 0.50 liters of solution. Kb of ammonia is 1.8 x 10‐5. Determine
the pH of this solution at equilibrium. (Hint: This is an ICE problem.)
9. Hydrazine, N2H4, has been used as a rocket fuel. Like ammonia, it is a Bronsted base. A 0.15 M solution has a pH of 10.70.
What is the Kb for hydrazine?
10. HF, hydrofluoric acid is a weak acid with a Ka of 3.55 x 10¯4. What would be the pH of a solution of 1.34 M lithium fluoride?
11. The Ka of citric acid (HC6H7O7) is 1.7 x 10¯4. What is the pH of 0.35 M solution of sodium citrate (NaC6H7O7)?
12. CH3NH2, methyl amine is a weak base with a Kb of 4.38 x 10¯4. What would be the pH of a solution of 0.350 M methyl
ammonium chloride, CH3NH3+Cl¯?
13. What is the pH of a 0.502 M solution of NH4NO3? The ionization constant of the weak base NH3 is 1.77 x 10¯5
18.4 Neutralization
Example Problem 6
Calculating Concentration from Titration Data
In a titration, 53.7 mL 0.100M HCl solution is needed to neutralize 80.0 mL of KOH solution. What is the molarity of the KOH solution?
Practice Problems
31.A 45.0-mL sample of nitric acid solution is neutralized by 119.4 mL 0.200M NaOH solution. What is the molarity of the nitric acid solution?
32.What is the molarity of a CsOH solution if 29.61 mL 0.2500M HCl is needed to neutralize 60.00 mL solution?
33.A 70.0-mL sample of sulfuric acid solution is neutralized by 256.3 mL 0.100M NaOH solution. What is the molarity of the sulfuric acid
solution? (Hint: Note the mole ratio of the reactants in the balanced chemical equation.)
34.Below is a pH curve from an acid-base titration. On it are labeled three points: X, Y, and Z.
a. ______________________________________ Which point represents the equivalence
point?
b. ______________________________________ At which point is there excess acid in
the system?
c. ______________________________________ At which point is there excess base in
the system?
d. ______________________________________ If the base solution is 0.250 M and there
is one equivalent of OH- ions for each mole of base, how many moles of OHions are consumed at the end point of the titration?
35. A standardized solution of 0.065 M HCl is titrated with a saturated solution of calcium hydroxide to determine its molarity and its
solubility. It takes 25.0 mL of the base to neutralize 10.0 mL of the acid.
a.
Write the balanced molecular equation for this neutralization reaction.
_________________________________ b. Determine the molarity of the Ca(OH)2 solution.
______________________________ c.Based on your answer to part b, calculate the solubility of the base in grams per liter of solution. (Hint:
What is the concentration of Ca(OH)2 in the saturated solution?)
36. It is possible to carry out a titration without any indicator. Instead, a pH probe is immersed in a beaker containing the solution of
unknown molarity, and a solution of known molarity is slowly added from a buret. Use the titration data below to answer the following
questions.
Volume of KOH(aq) in the beaker = 30.0 mL
Molarity of HCl(aq) in the buret = 0.50 M
At the instant pH falls from 10 to 4, the volume of acid added to KOH = 27.8 mL.
___________________________________ a. What is the mole ratio of chemical equivalents in this system?
___________________________________ b. Calculate the molarity of the KOH solution, based on the above data.
Chapter 18 Concept Review
37.Explain how a base in the Arrhenius model is different from a base in the Brønsted-Lowry model.
38.The Ka value for acid X is 8.5x10-4, while Ka for acid Y is 4.6x10-8. Explain what these Ka values tell you about the strengths of the two acids.
39.How does the pH of an aqueous solution change when there is a decrease in the concentration of hydroxide ions? Explain your answer.
40.Solution A has a pH of 9.0, and solution B has a pOH of 3.0. State whether each solution is acidic, basic, or neutral. Which solution has a
higher concentration of hydrogen ions?
41.What is the molarity of a solution of HCl if the pH of the solution is 2.00?
42.How can you detect the equivalence point of an acid-base titration?
43.A chemist prepares a buffer solution by dissolving sodium formate (NaHCOO) and another substance in water. What is the other substance
likely to be? Explain your answer.