Worksheet: Classifying Acids and Bases Based on Dissociation Constants

In this worksheet, we will practice classifying acids and bases as weak or strong based on their dissociation constants.

Q1:

The relative acid strengths of NH4+ and HCN can be determined by comparing their acid and base dissociation constants, 𝐾a and 𝐾b. HCN has a 𝐾a of 4.9×10 and NH3, the conjugate base of NH4+, has a 𝐾b of 1.8×10. Given that the self-ionization constant of water is 1.0×10, which compound is the stronger acid?

  • AMore information is needed.
  • B N H 4 + is the stronger acid.
  • C H C N is the stronger acid.
  • D H C N and NH4+ are equally strong acids.

Q2:

The odor of vinegar is due to the presence of acetic acid, CHCOH32, a weak acid. For a solution of acetic acid, which of the following is false?

  • A [ C H C O ] 2 2 > [CHCOH]32
  • B [ H O ] 3 + > [OH]
  • C [ H O ] 3 + [ C H C O ] 2 2
  • D [ C H C O H ] 3 2 > [HO]3+
  • E [ H O ] 2 > [CHCOH]32

Q3:

Household ammonia is a solution of the weak base NH3 in water. For a solution of ammonia, which of the following is false?

  • A [ N H ] 3 [ N H ] 4 +
  • B [ O H ] > [HO]3+
  • C [ N H ] 3 > [OH]
  • D [ H O ] 2 > [NH]3
  • E [ O H ] [ N H ] 4 +

Q4:

Which base, CHNH32 or (CH)NH32, is the stronger base at 25C? The 𝐾b of CHNH32 at this temperature is 4.4×10 and the 𝐾b of (CH)NH32 is 5.9×10.

  • A ( C H ) N H 3 2
  • BIt is impossible to tell without knowing at what concentration their basicity is measured.
  • C C H N H 3 2
  • DThey are both amines, and therefore they are equally strong bases.

Q5:

The active ingredient formed by aspirin in the body is salicylic acid, CHOH(COH)642. The carboxyl group (COH)2 acts as a weak acid. The phenol group (an OH group bonded to an aromatic ring) also acts as an acid, but a much weaker acid.

Which one of the following is false for a 0.001 M aqueous solution of salicylic acid?

  • A [ C H O ( C O H ) ] > [ C H O H ( C O ) ] 6 4 2 6 4 2
  • B [ C H O H ( C O ) ] > [ C H O ( C O H ) ] 6 4 2 6 4 2
  • C [ H O ] > [ O H ] 3 +
  • D [ C H O H ( C O H ) ] > [ C H O ( C O H ) ] 6 4 2 6 4 2

Q6:

Which is the stronger base, (CH)N33 or HBO23? The 𝐾b of (CH)N33 is 6.3×105 and the 𝐾a of HBO33 is 5.4×10.10

  • AIt is impossible to tell without knowing at what concentration their basicity is measured.
  • B ( C H ) N 3 3
  • C ( C H ) N 3 3 and HBOHBO2323HBO23HBO23 are equally strong bases.
  • D H B O 2 3

Q7:

A 5.16 g sample of NHCl4 was added to 20.0 mL of 1.00 MNaOH and the resulting solution was diluted to 0.100 L. The 𝐾b of NH3 is 1.8×10. Is the solution acidic, neutral, or basic?

  • AAcidic
  • BBasic
  • CNeutral

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