Acid–Base Chemistry - 5 STEPS TO A 5: 500 AP Chemistry Questions to Know by Test Day! (2012)

5 STEPS TO A 5: 500 AP Chemistry Questions to Know by Test Day! (2012)

Chapter 9. Acid–Base Chemistry (Questions 331–361)

Questions 331–334 refer to the following answer choices:

(A) Proton acceptor

(B) Proton donor

(C) Electron pair acceptor

(D) Electron pair donor

(E) Hydroxide generator

331. Bronsted–Lowry acid

332. Lewis base

333. Arrhenius base

334. Forms coordinate covalent bonds with acids

Questions 335–339 refer to aqueous solutions containing 1:1 mole ratios of the following pairs of substances. Assume all concentrations are 1 M.

(A) NH3 and H3CCOOH (acetic acid)

(B) KOH and NH3

(C) HCl and KCl

(D) H3PO4 and KH2PO4

(E) NH3 and NH4Cl

335. The solution with the highest pH

336. The solution with the lowest pH

337. The solution with the pH closest to neutral

338. A buffer at an alkaline pH

339. A buffer at an acidic pH

340. What is the H+ concentration of a 0.02-M nitrous acid (HNO2) solution? (The Ka for HNO2 is 4.5 × 10−4.)

(A) 2.25 × 10−2

(B) 3.0 × 10−3

(C) 5.1 × 10−4

(D) 9.0 × 10−6

(E) 2.6 × 10−7

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341. Which of the following statements is true of the reaction represented above?

(A) H2O is the conjugate acid of F.

(B) OH is the conjugate acid of H2O.

(C) HF is the conjugate base of F.

(D) HF and H2O are conjugate acid–base pairs.

(E) HF and H2O are both Bronsted–Lowry acids.

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342. In the reaction above, H2O acts as:

(A) An acid

(B) A base

(C) A conjugate acid

(D) An oxidizing agent

(E) A reducing agent

343. All of the following increase the strength of an oxyacid except:

(A) A strongly electronegative central atom

(B) Electronegative atoms bonded to the central atom

(C) Electronegative atoms bonded to atoms other than the central atom

(D) An increased number of oxygen atoms bonded to the central atom

(E) An increased number of hydrogens

344. It is possible to create all of the following solutions by mixing 0.25 M and 0.35 M HCl except:

(A) 0.34 M HCl

(B) 0.31 M HCl

(C) 0.29 M HCl

(D) 0.26 M HCl

(E) 0.24 M HCl

345. The acid dissociation constant for a weak monoprotic acid HA is 5.0 × 10−9. The pH of a 0.5 M HA solution is closest to:

(A) 2

(B) 3

(C) 4

(D) 5

(E) 6

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346. The reaction above represents a general equilibrium between monoprotic acids HX and HY. If the equilibrium constant for this reaction was 2.5 × 103, which of the following could be correctly concluded about the chemical species involved?

(A) HY is a stronger acid than HX.

(B) Y is a stronger base than X.

(C) HY is the conjugate base of Y.

(D) X is the conjugate acid of HX.

(E) The pH of a solution containing a 1:1 mole ratio of HX and Y is 7.

Questions 347–349 refer to the following titration.

A solution of a weak monoprotic acid is titrated with a 0.1-M strong base, NaOH. The titration curve is shown below.

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347. From the curve, what is the value of the pH where the number of moles of strong base added is equal to the number of moles of weak acid in the initial solution?

(A) 4.75

(B) 7.00

(C) 7.45

(D) 8.73

(E) 11.3

348. At which pH are the concentrations of the weak acid and its conjugate base approximately equal?

(A) 2.88

(B) 4.75

(C) 7.00

(D) 8.73

(E) 13.0

349. The buffer region of this titration curve can be found between which of the following pH values?

(A) 2.88 and 6.13

(B) 4.75 and 8.73

(C) 6.13 and 11.29

(D) 8.73 and 11.29

(E) 11.29 and 12.25

350. Which of the following solutions at a concentration of 0.1 M has a pH > 7?

(A) NaCl

(B) KI

(C) HC2H3O2

(D) LiF

(E) NaBr

351. Which of the following is the conjugate acid of NH3?

(A) H+

(B) N2

(C) NH2

(D) NH3+

(E) NH4+

352. At 25°C, aqueous solutions with a pH of 6 have a hydroxide ion concentration, [OH], of:

(A) 1 × 10−6 M

(B) 1 × 10−8 M

(C) 0.006 M

(D) 6 M

(E) 8 M

353. Which of the following steps would convert 100 mL of KOH solution with a pH of 13 to a KOH solution with a pH of 12?

(A) Dilute the solution by adding 10 mL of distilled water.

(B) Dilute the solution by adding 900 mL of distilled water.

(C) Dilute the solution with an equal amount of KOH solution with a pH of 1.

(D) Add 10 mL of 1 M HCl solution.

(E) Add 100 mL of 1 M HCl solution.

354. Citric acid (H3C6H5O7) is a triprotic acid with K1 = 8.4 × 10−4, K2 = 1.8 × 10−5, and K3 = 4.0 × 10−6. In a 0.01-M aqueous solution of citric acid, which of the following species is present in the lowest concentration?

(A) H3O+(l)

(B) H3C6H5O7(aq)

(C) H2C6H5O7(aq)

(D) H1C6H5O72–(aq)

(E) C6H5O73–(aq)

355. Mixtures that would be useful as buffers include which of the following?

I. NH3 and NH4Cl

II. HCl and KCl

III. HF and KF

(A) I only

(B) I and II only

(C) I and III only

(D) II and III only

(E) I, II, and III

356. A sample of 200 mL of 0.20 M Sr(OH)2 is added to 800 mL of 0.80 M Ba(OH)2. Which of the following best approximates the pH of the final solution?

(A) 0

(B) 1

(C) 12

(D) 13

(E) 14

357. The pH of a solution prepared by the addition of 100 mL 0.002 M HCl to 100-mL distilled water is closest to:

(A) 1.0

(B) 1.5

(C) 2.0

(D) 3.0

(E) 4.0

358. The pH of a solution prepared by the addition of 5.0 mL 0.02 M Ba(OH)2 to 15-mL distilled water is closest to:

(A) 2.0

(B) 4.0

(C) 11.0

(D) 12.0

(E) 13.0

Questions 359–361 refer to the figures below. The figures show a burette used in the titration of an acid with a 0.5-M solution of Sr(OH)2. Figure 1 shows the level of Sr(OH)2 at the start of the titration and Figure 2 shows the level of Sr(OH)2 at the end of the titration. The indicator used in this experiment was phenophthalein.

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359. What evidence indicates that the endpoint of the titration has been reached?

(A) The color of the solution in the burette changes from colorless to pink.

(B) The color of the solution in the burette changes from pink to colorless.

(C) The color of the solution in the flask below changes from colorless to pink.

(D) The color of the solution in the flask below changes from pink to colorless.

(E) The pH of the solution does not change.

360. The volume of Sr(OH)2 used to neutralize the acid was closest to:

(A) 3.5 mL

(B) 10.60 mL

(C) 31.80 mL

(D) 42.04 mL

(E) 42.40 mL

361. In a different titration, 25 mL of the same 0.5 M Sr(OH)2 solution was used to titrate 35 mL HCl solution to the equivalence point. What is the molarity of the HCl solution?

(A) 0.5 M

(B) 0.7 M

(C) 1.4 M

(D) 2.1 M

(E) 2.8 M