Chapter.8 Test Questions & Answers Acids and Bases

General, Organic, and Biochemistry, 10e (Denniston)

Chapter 8 Acids and Bases

1) Which of the following statements concerning acids and bases is FALSE?

A) A Brønsted-Lowry acid is a proton (H+) donor.

B) A Brønsted-Lowry base is a proton (H+) acceptor.

C) Reactions between acids and bases involve the transfer of a proton (H+) from the acid to the base.

D) Addition of an acid to water decreases the pH of the solution.

E) Addition of a base to water increases the hydronium ion concentration of the solution.

2) Which statement correctly describes conjugate acids and bases according to the Brønsted-Lowry theory?

A) A conjugate base is the species formed when an acid donates a proton; a conjugate acid is the species formed when a base accepts a proton.

B) A conjugate base is the species formed when an acid accepts a proton; a conjugate acid is the species formed when a base donates a proton.

C) A conjugate acid is the species formed when an acid donates a proton; a conjugate base is the species formed when a base accepts a proton.

D) A conjugate acid is an acid that does not completely transfer a proton to water; a conjugate base is a base that does not completely accept a proton from water.

E) A conjugate acid is the solution formed when an acid is added to water; a conjugate base is the solution formed when a base is added to water.

3) Which statement concerning the relative strength of acids is FALSE?

A) Strong and weak acids differ in their extent of proton transfer to water.

B) Strong acids are good proton donors; weak acids are poor proton donors.

C) A strong acid completely transfers its protons to water; a weak acid only partially transfers its protons to water.

D) Strong acids produce strong conjugate bases; weak acids produce weak conjugate bases.

E) A strong acid produces more hydronium ions in water than a weak acid of the same concentration.

4) Which of the following best represents the autoionization, or self-ionization, of water?

A) H2O(l) → H+(aq) + OH-(aq)

B) 2H2O(l)2H2(aq) + O2(aq)

C) 2H2O(l)H3O+(aq) + OH-(aq)

D) H2O(l) → H2(aq) + O2-(aq)

E) H+(aq) + OH-(aq) → H2O(l)

5) Which of the following correctly describes what is meant by the term neutralization?

A) the reaction between hydroxide (OH−) and water to form a base

B) the reaction between a proton (H+) and water to form a hydronium ion (H3O+)

C) the reaction between an acid and a base to form a salt and water

D) the reaction between two molecules of water, one acting as an acid and the other acting as a base

E) the reaction between an oxidizing agent and a reducing agent

6) What is always a characteristic of a solution that contains a buffer?

A) The solution is neutral and has a pH of 7.

B) The solution contains a small amount of solute dissolved in a large volume of solvent.

C) The solution has been diluted by the addition of solvent.

D) The solution resists large changes in pH when small amounts of acids or bases are added.

E) The solution maintains a constant pH value; no amount of added acid or base can change the pH.

7) Consider the following generalized buffer solution equilibrium: 

BH+(aq) + H2O(l) H3O+(aq) + B(aq) 

When a small amount of a strong base such as sodium hydroxide is added to the solution, which of the four species shown would experience an increase in concentration? (Hint: Use LeChatelier's principle.)

A) BH+

B) H2O

C) H3O+

D) B

E) None of the species would increase in concentration.

8) What is TRUE about a solution whose pH is less than 7?

A) It has a hydronium ion concentration less than 1 × 10−7.

B) It has a hydronium ion concentration that is higher than pure water itself.

C) It has a hydroxide ion concentration equal to its hydronium ion concentration.

D) It is a solution that requires a buffer.

E) It is a basic solution.

9) A particular buffer solution consists of a weak acid and its conjugate base. How could this buffer solution be modified so as to increase its buffer capacity against added base?

A) Increase the concentration of the weak acid.

B) Increase the concentration of its conjugate base.

C) Use a strong base and its conjugate acid instead.

D) Use a strong acid and its conjugate base instead.

E) Make the concentrations of the weak acid and its conjugate base equal.

10) A buffer solution contains acetic acid (HC2H3O2) at a concentration of 0.225 M and sodium acetate (NaC2H3O2) at a concentration of 0.164 M. The value of Ka for acetic acid is 1.75 × 10−5. What is the pH of this buffer solution?

A) 0.137

B) 0.862

C) 2.40

D) 4.62

E) 4.76

11) Formic acid (HCO2H) is a weak acid found in the venom of bees and ant stings. Which of the following is an accurate statement concerning an aqueous solution of formic acid? 

HCO2H(aq) + H2O(l)H3O+(aq) + HCO2−(aq)      Ka = 1.8 × 10−4

A) The reaction between formic acid and water is slow, due to the low value for Ka.

B) A formic acid solution predominantly contains undissociated HCO2H molecules.

C) A formic acid solution predominantly contains H3O+ and HCO2− ions.

D) A formic acid solution contains a greater concentration of dissolved ions than it does neutral formic acid molecules.

E) A formic acid solution contains equal amounts of H3O+ and HCO2H.

12) HCl is a strong electrolyte. A bottle of HCl contains the label 0.015 M HCl(aq). Which statement concerning this HCl solution is FALSE?

A) The solution is acidic.

B) The pH of the solution is 1.5.

C) The hydronium ion concentration in this solution is 0.015 M.

D) The solution has a higher concentration of hydronium ions than hydroxide ions.

E) The solution contains dissolved H3O+ and Cl− ions only; no HCl molecules are present.

13) The species that remains after an acid donates a proton is called its conjugate base. What is the conjugate base of the hydronium ion, H3O+?

A) OH-

B) H2O-

C) H2O

D) H2O+

E) H3O+ has no conjugate base.

14) What is the conjugate acid of NH2−?

A) NH2−

B) NH3

C) NH4+

D) NH2+

E) NH4−

15) What is the conjugate base of H2SO4?

A) SO42−

B) HSO4−

C) H2SO3

D) SO4−

E) H2PO4+

16) Butyric acid is a weak acid. Which reaction equation properly represents the dissociation of butyric acid in water?

A) CH3CH2CH2COOH(aq) + H2O(l) → CH3CH2CH2COO- (aq) + H3O+(aq)

B) CH3CH2CH2COOH(aq) + H2O(l) CH3CH2CH2COO-(aq) + H3O+(aq)

C) CH3CH2CH2COOH(aq) + H2O(l) → CH3CH2CH2COOH2+(aq) + OH-(aq)

D) CH3CH2CH2COOH(aq) + H2O(l) CH2CH2CH2COOH(aq) + H3O+(aq)

E) CH3CH2CH2COOH(aq) + H2O(l) → CH3CH2CH2COO- (aq) + H3O+(aq) and CH3CH2CH2COOH(aq) + H2O(l) CH3CH2CH2COO-(aq) + H3O+(aq) are correct.

17) A sample of black coffee was measured to have [H3O+] = 7.94 × 10−6. What is TRUE about this solution?

A) The solution is acidic.

B) The solution contains less hydronium ions than pure water itself.

C) The solution does not contain any OH−ions.

D) The solution has [OH−] = 7.94 × 10−6.

E) The pH of the solution is 7.94.

18) Which of the following is an example of a diprotic acid?

A) NH2−

B) H2SO4

C) HCl

D) CH4

E) NH2− and H2SO4 are correct.

19) A buffer solution contains carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3), each at a concentration of 0.100 M. The relevant equilibrium is shown below. What is the pH of this buffer solution? 

H2CO3(aq) + H2O(l) H3O+(aq) + HCO3−(aq)   Ka = 4.5 × 10−7

A) 4.50

B) 7.00

C) 6.35

D) 7.65

E) 2.16

20) For the reaction shown below, which of the following correctly represents a conjugate acid-base pair?

HCO2H(aq) + H2O(l) H3O+(aq) + HCO2−(aq)

A) HCO2H/H3O+

B) HCO2H/H2O

C) H2O/HCO2-

D) H3O+/HCO2-

E) HCO2H/HCO2−

21) Consider two beakers, one containing 1.0 M HCl and the other containing 1.0 M CH3COOH. Which solution would have the lowest pH?

A) 1.0 M CH3COOH because its solution contains a lower hydronium ion concentration than 1.0 M HCl

B) 1.0 M HCl because its solution contains a higher hydronium ion concentration than 1.0 M CH3COOH

C) 1.0 M HCl because its solution contains a lower hydronium ion concentration than 1.0 M CH3COOH

D) 1.0 M CH3COOH because its solution contains a higher hydronium ion concentration than 1.0 M HCl

E) Both solutions would have the same pH because they have the same concentration.

22) Titration of 15.0 mL of an NaOH solution required 7.4 mL of a 0.25 M KNO3 solution. What is the molarity of the NaOH solution?

A) 0.25 M

B) 0.017 M

C) 0.12 M

D) 0.44 M

E) 0.0019 M

23) An aqueous solution with a low pH is necessary for a certain industrial process. Which of the following solutions would have the lowest pH?

A) 2.0 M NaOH

B) 0.5 M HCl

C) 1.0 M acetic acid

D) 1.0 M HCl

E) All solutions would have the same pH.

24) Which one of the following is NOT a characteristic property of a base?

A) tastes bitter

B) feels slippery

C) increases [H+] in water

D) is corrosive

E) causes many metal ions to precipitate

25) Which one of the following correctly represents a conjugate acid-base pair?

A) H2O, O-

B) H3O+, OH-

C) H2CO3, CO32-

D) HCl, Cl2

E) H2CO3, HCO3-

26) What is the hydronium ion concentration of pure water at 25°C?

A) 7.0 × 107 M

B) 7.0 × 10−7 M

C) 1.0 × 107 M

D) 1.0 × 10−7 M

E) 1.0 × 10−14 M

27) If the hydronium ion concentration of an aqueous solution at 25°C is 5 × 10−6 M, what is the hydroxide ion concentration?

A) 2 × 10−10 M

B) 2 × 10−9 M

C) 2 × 10−8 M

D) 2 × 107 M

E) 2 × 1019 M

28) What is the hydronium ion concentration of a solution with a pH of 6.0?

A) 1 × 106 M

B) 1 × 10−6 M

C) 6 × 101 M

D) 6 × 10−1 M

E) 6 × 10−14 M

29) What is the pH of a 1.0 × 10−4 M solution of KOH?

A) 4.00

B) 6.00

C) 7.00

D) 10.00

E) 14.00

30) What is the pH of a solution that has [H3O+] = 6.0 × 10−3 M?

A) 1.7 × 10−12

B) 2.22

C) 3.60

D) 5.12

E) 11.78

31) Titration of 25.0 mL of an HCl solution of unknown concentration requires 14.8 mL of 0.100 M NaOH. What is the molar concentration of the HCl solution? NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

A) 0.592 M

B) 5.87 M

C) 0.0592 M

D) 0.0692 M

E) 1.25 M

32) The reaction of an acid with a base produces a salt and another product. What is the identity of the other product?

A) hydronium ion

B) water

C) a buffer

D) a proton

E) hydroxide ion

33) A solution containing a buffer has an initial pH of 8.78. If a student adds 5 drops of HCl(aq) to this solution, what would be a reasonable pH for the resulting solution?

A) 5.22

B) 7.00

C) 8.64

D) 8.78

E) 8.89

34) A solution containing a buffer has an initial pH of 8.78. If a student adds 5 drops of NaOH(aq) to this solution, what would be a reasonable pH for the resulting solution?

A) 7.00

B) 8.64

C) 8.78

D) 8.89

E) 12.25

35) A solution containing a buffer has an initial pH of 8.78. If a student adds 5 drops of NaCl(aq) to this solution, what would be a reasonable pH for the resulting solution?

A) 5.22

B) 7.00

C) 8.64

D) 8.78

E) 8.89

36) Sodium hydroxide (NaOH) can react with phosphoric acid (H3PO4) in a neutralization reaction. What is the reacting ratio of NaOH to H3PO4?

A) 1:1

B) 1:3

C) 3:8

D) 2:7

E) 3:1

37) Morphine is used medicinally as a pain reliever. If an aqueous solution of morphine has [H3O+] = 1.1 × 10−10 M, what is the pH of this solution?

A) 1.00

B) 3.69

C) 8.96

D) 9.96

E) 11

38) What term is used to describe the amount of strong acid or strong base that can be added to a buffer solution without significantly changing its pH?

A) buffer threshold

B) Henderson-Hasselbalch strength

C) conjugate acid-base capacity

D) buffer capacity

E) acid dissociation constant

39) For the reaction shown below, which of the following is a conjugate acid-base pair?

C5H5N(aq) + H2O(l)C5H5NH+(aq) + OH−(aq)

A) C5H5N, H2O

B) C5H5N, C5H5NH+

C) C5H5NH+, OH−

D) H2O, OH−

E) C5H5N, C5H5NH+ and H2O, OH−

40) A patient's urine sample gave a reading of pH = 8.2. What is the value of [H3O+] in this solution?

A) 6.0 × 10-9 M

B) 0.91 M

C) 1.6 × 10-8 M

D) 1.6 × 108 M

E) 2.7 × 10-4 M

41) Calculate the molar concentration of a sodium hydroxide solution if 60.00 mL of this solution were required to neutralize 30.00 mL of a 0.150 M hydrochloric acid solution. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

A) 3.00 M

B) 6.00 M

C) 0.0750 M

D) 0.150 M

E) 2.25 M

42) A buffer solution is prepared by placing twice the concentration of propanoic acid (C2H5COOH, Ka=1.34 ×10−5) as the concentration of its conjugate base sodium propanoate into a flask. The pH of the resulting buffer solution is best described as which of the following?

A) less than 4.87

B) 4.87

C) between 4.87 and 9.00

D) greater than 11.00

E) Undeterminable; the concentrations of the acid and conjugate base must be given.

43) Which of the following compounds is NOT considered a polyprotic acid?

A) H2SO4

B) H3PO4

C) H2CO3

D) H2SO3

E) CH3COOH

44) What is the pH of a 0.035 M HCl solution?

A) 3.50

B) 1.46

C) 2.27

D) 5.59

E) 12.54

45) What is the [OH−] of a solution that has a pH = 10.95?

A) 1.03 M

B) 1.1 × 10-11 M

C) 8.9 × 10-4 M

D) 3.05 M

E) 7.4 × 10-5 M

46) According to Arrhenius' theory of acids and bases, acids increase the hydrogen ion concentration in water.

47) All Brønsted-Lowry acids contain at least one hydrogen atom.

48) All Brønsted-Lowry bases contain hydroxide.

49) The addition of an acid to water increases the [H3O+] and decreases the pH.

50) Nitric acid is a strong acid and dissociates completely when dissolved in water.

51) Strong acids are completely dissociated when dissolved in water.

52) All metal hydroxides are strong bases.

53) The concentration of a weak acid or base affects its degree of dissociation in water.

54) The ion-product of water is affected by a change in temperature.

55) A pH of 0 is considered neutral.

56) A standard solution is a solution whose concentration is accurately known.

57) The main buffer system found in blood is the HCl/Cl− system.

58) The combination of a weak acid and a strong acid form a buffer solution.

59) All buffer solutions operate at a pH at or near 7.

60) A hydronium ion is a protonated water molecule.

61) The pH of a 12.0 M solution of HCl is 1.1.

62) Which of the following statements concerning a voltaic cell is FALSE?

A) The oxidation half reaction occurs at the cathode.

B) A voltaic cell uses an oxidation-reduction reaction to produce electrical energy.

C) The cell consists of two half cells.

D) The anode and the cathode are separated by a salt bridge.

E) At the anode a substance will lose electrons.

63) Choose the best classification of the reaction represented by the following equation: C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l)

A) combustion

B) acid-base

C) precipitation

D) decomposition

E) combination

64) In electrolysis, electrical energy is used to drive a non-spontaneous oxidation-reduction reaction to occur.

65) What is the general term for the process in which a chemical species loses electrons?

A) oxidation

B) reduction

C) condensation

D) Lewis base

E) decomposition

66) Which statement correctly describes what is happening in the reaction shown below? 2Mg(s) + S2(g) → MgS(s)

A) Mg is oxidized.

B) S2 loses electrons.

C) MgS is the reducing agent.

D) Mg is the oxidizing agent.

E) MgS gains electrons.

67) During an oxidation-reduction reaction, the oxidizing agent loses electrons.