Ch. 15 – Acids and Bases Practice Questions
1. Calculate the concentration of hydronium ions in each solution.
(a) 4.5 mol/L HCl(aq)
(b) 30.0 mL of 4.50 mol/L HBr (aq)diluted to 100.0 mL
(c) 18.6 mL of 2.60 mol/L HClO4 (aq)added to 24.8 mL of 1.92 mol/L NaOH(aq)
(d) 17.9 mL of 0.175 mol/L HNO3 (aq)added to 35.4 mL of 0.0160 mol/L Ca(OH)2(aq)
2. Calculate the concentration of hydroxide ions in each solution.
(a) 3.1 mol/L KOH(aq)
(b) 21.0 mL of 3.1 mol/L KOH diluted to 75.0 mL
(c) 23.2 mL of 1.58 mol/L HCl (aq)added to 18.9 mL of 3.50 mol/L NaOH(aq)
(d) 16.5 mL of 1.50 mol/L H2SO4 (aq) added to 12.7 mL of 5.50 mol/L NaOH (aq)
3. Determine whether reacting each pair of solutions results in an acidic solution or a basic solution. Then
calculate the concentration of the ion that causes the solution to be acidic or basic. (Assume that the volumes in
part (a) are additive. Assume that the volumes in part (b) stay the same.) Determine the final pH in each case.
(a) 31.9 mL of 2.75 mol/L HCl (aq) added to 125 mL of 0.0500 mol/L Mg(OH)2 (aq)
(b) 4.87 g of NaOH(S)added to 80.0 mL of 3.50 mol/L HBr (aq)
4. 2.75 g of MgO(S) is added to 70.0 mL of 2.40 mol/L HNO3 (aq). Is the solution that results from the reaction
acidic or basic? What is the concentration of the ion that is responsible for the character of the solution? What is
the pH of the solution?
5. Calculate the pH of a sample of vinegar that contains 0.83 mol/L acetic acid. What is the percent dissociation
of the vinegar?
6. In low doses, barbiturates act as sedatives. Barbiturates are made from barbituric acid, a weak monoprotic
acid that was first prepared by the German chemist Adolph von Baeyer in 1864. The formula of barbituric acid
is C4H4N2O3. A chemist prepares a 0.10 mol/L solution of barbituric acid. The chemist finds the pH of the
solution to be 2.50. What is the acid dissociation constant for barbituric acid? What percent of its molecules
dissociate?
7. A solution of hydrofluoric acid has a molar concentration of 0.0100 mol/L. What is the pH of this solution?
8. Hypochlorous acid, HOCl, is used as a bleach and a germ-killer. A chemist finds that 0.027% of
hypochlorous acid molecules are dissociated in a 0.40 mol/L solution of the acid. What is the value of Ka for the
acid?
9. The word “butter” comes from the Greek butyros. Butanoic acid (common name: butyric acid) gives rancid
butter its distinctive odour. Calculate the pH of a 1.0 x 10−2 mol/L solution of butanoic acid (Ka =1.51 x 10−5).
10. Caproic acid, C5H11COOH, occurs naturally in coconut and palm oil. It is a weak monoprotic acid, with
Ka = 1.3 x 10−5. A certain aqueous solution of caproic acid has a pH of 2.94. How much acid was dissolved to
make 100 mL of this solution?
11. An aqueous solution of household ammonia has a molar concentration of 0.105 mol/L. Calculate the pH of
the solution.
12. Hydrazine, N2H4, has been used as a rocket fuel. The concentration of an aqueous solution of hydrazine is
5.9 x10 −2 mol/L. Calculate the pH of the solution.
13. Morphine, C17H19NO3, is a naturally occurring base that is used to control pain. A 4.5 x 10−3 mol/L solution
has a pH of 9.93. Calculate Kb for morphine.
14. Methylamine, CH3NH2, is a fishy-smelling gas at room temperature. It is used to manufacture several
prescription drugs, including methamphetamine. Calculate [OH−] and pOH of a 0.25 mol/L aqueous solution of
methylamine.
15. At room temperature, trimethylamine, (CH3) 3N, is a gas with a strong ammonia-like odour. Calculate [OH−]
and the percent of trimethylamine molecules that react with water in a 0.22 mol/L aqueous solution.
16. An aqueous solution of ammonia has a pH of 10.85. What is the concentration of the solution?
Chapter 15 Questions
17. 17.85 mL of nitric acid neutralizes 25.00 mL of 0.150 mol/L NaOH(aq). What is the concentration of the
nitric acid?
(Ans: 0.210 M)
18. What volume of 1.015 mol/L magnesium hydroxide is needed to neutralize 40.0 mL of 1.60 mol/L
hydrochloric acid?
(Ans: 31.5 mL)
19. What volume of 0.150 mol/L hydrochloric acid is needed to neutralize each solution below?
(a) 25.0 mL of 0.135 mol/L sodium hydroxide
(Ans: 22..5 mL)
(b) 20.0 mL of 0.185 mol/L ammonium hydroxide
(Ans: 24..7 mL)
(c) 80 mL of 0.0045 mol/L calcium hydroxide
(Ans: 4..8 mL)
20. What concentration of sodium hydroxide solution is needed for each neutralization reaction?
(a) 37.82 mL of sodium hydroxide neutralizes 15.00 mL of 0.250 mol/L hydrofluoric acid. (Ans: 0.09915 M)
(b) 21.56 mL of sodium hydroxide neutralizes 20.00 mL of 0.145 mol/L sulfuric acid. (Ans: 0.2690 M)
(c) 14.27 mL of sodium hydroxide neutralizes 25.00 mL of 0.105 mol/L phosphoric acid (Ans: 0.5519 M)
21. Write balanced stepwise net ionic equations and the overall equation for the reaction between the following
substances in aqueous solution:
(a) sodium thiosulfate and excess hydronium ions (b) carbonic acid and excess hydroxide ions
22. Sodium carbonate solution, Na2CO3(aq), is a common primary standard for acid titrants. Write reactions
showing the quantitative transfer of protons from the hydronium ions of a strong acid to the sodium carbonate,
and the overall reaction for the titration.
23. Write the stepwise reactions that occur for the proton transfers between sulfurous acid and sodium
hydroxide, and write the overall neutralization reaction.
Section 1 Review
1. Distinguish between a concentrated solution of a weak base and a dilute solution of a strong base. Give an
example of each.
2. Lactic acid, CH3CHOHCOOH, is a monoprotic acid that is produced by muscle activity. It is also produced
from milk by the action of certain kinds of bacteria. What is the pH of a 0.12 M solution of lactic acid?
3. A 0.10 mol/L solution of a weak acid was found to be 5.0% dissociated. Calculate Ka.
4. Phenol, C6H5OH, is an aromatic alcohol with weak basic properties. It is used as a disinfectant and cleanser.
Calculate the molar concentration of OH− ions in a 0.75 mol/L solution of phenolate, C6H5O−, ions
(Kb = 7.7 × 10−5). What is the pH of the solution?
5. Potassium sorbate is a common additive in foods. It is used to inhibit the formation of mould. A solution
contains 1.82 g of sorbate, C6H7O2- , ions (Ka = 1.7 × 10−5) dissolved in 250 mL of water. What is the pH of
the solution?
6. Write the chemical formula for the conjugate base of hypobromous acid, HOBr. Calculate Kb for this ion.
7. Describe how a buffer solution differs from an aqueous acidic or basic solution.
8. Explain the function and importance of buffers in blood.
9. Explain why an aqueous mixture of NaCl and HCl does not act as a buffer, but an aqueous mixture of NH3
and NH4Cl does.
10. In Photo A below, the pH of a 100 mL sample of dilute HCl(aq) reads 5.00. In Photo B, the pH of a 100 mL
sample of solution containing a mixture of 1 mol/L acetic acid and 1 mol/L sodium acetate also reads 5.00. The
left side of Photo B shows the pH of the dilute HCl(aq) solution after 1 mL of 1 mol/L hydrochloric acid was
added. The right side of the photo shows the pH after 1 mL of 1 mol/L sodium hydroxide was added. In Photo
D, 1 mL of 1 mol/L hydrochloric acid (left) and 1 mL of 1 mol/L sodium hydroxide (right) have been added to
the acetic acid-sodium acetate mixture. Examine the pH readings in Photos B and D and explain the results.
Section 2 Review
1. Write a generalized word equation to describe what happens during a neutralization reaction.
2. Write a chemical equation for each neutralization reaction.
(a) KOH with HNO3
(c) H3PO4 with NaOH
(b) HBr with Ca(OH)2
(d) Mg(OH) 2 with HCl
3. (a) Distinguish between the equivalence point and the end point for a titration.
(b) When choosing an indicator, do the pH values of the two points need to coincide exactly? Explain.
4. Sketch the pH curve for the titration of a weak acid with a strong base. Show the equivalence point on your
sketch. Suggest an indicator that might be used, and explain your selection.
5. Suggest an indicator that could be used for the titration of potassium hydroxide with nitrous acid. Explain
your suggestion.
6. A 25.0 mL sample of sulfuric acid is completely neutralized by adding 32.8 mL of 0.116 mol/L ammonia
solution. Ammonium sulfate, (NH4)2SO4, and water are formed. What is the concentration of the
sulfuric acid?
7. The following data were collected during a titration. Calculate the concentration of the sodium hydroxide
solution.
Volume of HCl (aq)
10.00 mL
Final volume of NaOH (aq)
23.08 mL
Initial volume of NaOH (aq)
1.06 mL
Concentration of HCl (aq)
0.235 mol/L
8. Estimate the pH of a solution in which bromocresol green is blue, and methyl red is orange.
9. Classify these substances in aqueous solution as monoprotic, diprotic, triprotic, monobasic, dibasic, or
tribasic.
(a) H2S
(b) HNO3
(c) CrO4
(d) H3P
(e) CH3COOH2−
(f) HOOCCOOH
10. Sketch the curve for a titration of a polyprotic substance titrated with a strong base. How does it compare
with the curve for a polybasic substance titrated with a strong acid?