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AP®ChemistryCollege BoardExam QuestionsUnit 8: Acids & BasesAcids & Bases

Acids & Bases (College Board AP® Chemistry)

Exam Questions

38 mins14 questions

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Acids & Bases

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Acids & Bases

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11 mark

Which of the following is the acid dissociation, Ka, constant for ethanoic acid? 

  • CH3COOH 

  • fraction numerator left square bracket CH subscript 3 COO to the power of minus right square bracket left square bracket straight H to the power of plus right square bracket over denominator left square bracket CH subscript 3 COOH right square bracket end fraction

  • fraction numerator left square bracket CH subscript 3 COOH right square bracket over denominator left square bracket CH subscript 3 COO to the power of minus right square bracket left square bracket straight H to the power of plus right square bracket end fraction

  • left square bracket CH subscript 3 COO to the power of minus right square bracket left square bracket straight H to the power of plus right square bracket

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21 mark

What is the correct expression for the base dissociation constant, Kb, for propylamine?

  • Kb = begin mathsize 14px style fraction numerator left square bracket C H subscript 3 C H subscript 2 C H subscript 2 N H subscript 3 to the power of plus right square bracket open square brackets O H to the power of minus sign close square brackets over denominator open square brackets C H subscript 3 C H subscript 2 C H subscript 2 N H subscript 2 close square brackets end fraction end style

  • Kb = begin mathsize 14px style fraction numerator left square bracket C H subscript 3 C H subscript 2 C H subscript 2 N H subscript 3 to the power of plus right square bracket open square brackets H subscript 2 O close square brackets over denominator open square brackets C H subscript 3 C H subscript 2 C H subscript 2 N H subscript 2 close square brackets end fraction end style

  • Kb = begin mathsize 14px style fraction numerator left square bracket C H subscript 3 C H subscript 2 C H subscript 2 N H subscript 3 to the power of plus right square bracket open square brackets O H to the power of minus sign close square brackets over denominator open square brackets C H subscript 3 C H subscript 2 C H subscript 2 N H subscript 2 close square brackets open square brackets H subscript 2 O close square brackets end fraction end style

  • Kb = begin mathsize 14px style left square bracket C H subscript 3 C H subscript 2 C H subscript 2 N H subscript 3 to the power of plus right square bracket open square brackets O H to the power of minus sign close square brackets end style

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31 mark

In the nitration of benzene, concentrated sulfuric acid and nitric acid are mixed to form the nitronium ion (NO2+), the electrophile in the reaction:

H2SO4 + HNO3 ⇋  H2NO3+ + HSO4-

Which two species are correctly identified as Brønsted–Lowry bases?

  • H2NO3+ and HSO4-

  • HNO3 and H2NO3+

  • H2SO4 and HSO4-

  •  

    HNO3 and HSO4-

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41 mark

In the equilibrium reaction below:

H3NSO3 (aq) + 2NH3 (aq) ⇌ HNSO32- (aq) + 2NH4+ (aq)

Which two species are correctly identified as Brønsted–Lowry acids in this reaction?

  • NH4+ and NH3

  • NH4+ and HNSO32-

  • H3NSO3 and HNSO32-

  • H3NSO3 and NH4+

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11 mark

25.00 mL of 0.25 M nitric acid is added to 12.50 mL of 0.10 M sodium hydroxide.

What is the pH of the resulting mixture?

  • 2.30

  • 0.60 

  • 0.88

  • 13.00

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21 mark

HF (aq) ⇌ H+ (aq) + F (aq) Ka = 6.3 x 10-4

On the basis of the information above, what is the approximate percent ionization of HF in a 0.25 M HF (aq) solution?

  • 0.05%

  • 5.2%

  • 0.063%

  • 6.3 x 10-4%

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31 mark

For the species HPO42−​, consider the following reactions:

  1. HPO42− + H+ → H2PO4−​

  2. HPO42− → H+ + PO43−​

Based on these reactions, which of the following statements is correct?

  • HPO42− is only amphoteric, not amphiprotic.

  • HPO42− is only amphiprotic, not amphoteric.

  • HPO42− is both amphiprotic and amphoteric.

  • HPO42− is neither amphiprotic nor amphoteric.

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41 mark

Phenol (C6H5OH) is an aromatic compound with a hydroxyl group attached to a benzene ring. It behaves as a weak acid by donating a proton to form a conjugate base.

What is the correct formula of the conjugate base of phenol?

  • C6H4-OH 

  • C6H5OH2+

  • C6H5O-

  • C6H6+OH 

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51 mark

Phosphoric acid (H3PO4​) is a polyprotic acid that can dissociate to form amphiprotic species.

Which of the following species are amphiprotic?

  • HPO42− and H2PO4−

  • H2PO4− and PO43−

  • H3PO4​ and HPO42−

  • HPO42− and PO43−

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11 mark

What is the approximate pH of 0.50 M benzoic acid, C6H5COOH (aq)?

Ka of C6H5COOH = 6.3 x 10-5

  • 4.50

  • 4.20

  • 0.30

  • 2.25

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