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Worksheet: Comparing Ionization Constants

Q1:

A 5.16 g sample of N H C l 4 was added to 20.0 mL of 1 . 0 0 M N a O H and the resulting solution diluted to 0.100 L. The 𝐾 b of N H 3 is 1 . 8 Γ— 1 0 βˆ’ 5 . Is the solution acidic, neutral, or basic?

  • ANeutral
  • BAcidic
  • CBasic

Q2:

Which base, C H N H 3 2 or ( C H ) N H 3 2 , is the stronger base at 2 5 ∘ C ? The 𝐾 b of C H N H 3 2 at this temperature is 4 . 4 Γ— 1 0 βˆ’ 4 and the 𝐾 b of ( C H ) N H 3 2 is 5 . 9 Γ— 1 0 βˆ’ 4 .

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

Q3:

The relative acid strengths of N H 4 + and H C N can be determined by comparing their acid and base dissociation constants, 𝐾 a and 𝐾 b . H C N has a 𝐾 a of 4 . 9 Γ— 1 0 βˆ’ 1 0 and N H 3 , the conjugate base of N H 4 + , has a 𝐾 b of 1 . 8 Γ— 1 0 βˆ’ 5 . Given that the self-ionization constant of water is 1 . 0 Γ— 1 0 βˆ’ 1 4 , which compound is the stronger acid?

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

Q4:

Household ammonia is a solution of the weak base N H 3 in water. For a solution of ammonia, which of the following is false?

  • A [ N H ] 3 > [ O H ] –
  • B [ O H ] – β‰ˆ [ N H ] 4 +
  • C [ O H ] – > [ H O ] 3 +
  • D [ N H ] 3 β‰ˆ [ N H ] 4 +
  • E [ H O ] 2 > [ N H ] 3

Q5:

The odor of vinegar is due to the presence of acetic acid, C H C O H 3 2 , a weak acid. For a solution of acetic acid, which of the following is false?

  • A [ C H C O H ] 3 2 > [ H O ] 3 +
  • B [ H O ] 3 + β‰ˆ [ C H C O ] 2 2 –
  • C [ H O ] 2 > [ C H C O H ] 3 2
  • D [ C H C O ] 2 2 – > [ C H C O H ] 3 2
  • E [ H O ] 3 + > [ O H ] –

Q6:

The active ingredient formed by aspirin in the body is salicylic acid, C H O H ( C O H ) 6 4 2 . The carboxyl group ( C O H ) 2 acts as a weak acid. The phenol group (an O H 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 H ( C O H ) ] > [ C H O ( C O H ) ] 6 4 2 6 4 2 –
  • B [ H O ] > [ O H ] 3 + –
  • C [ C H O H ( C O ) ] > [ C H O ( C O H ) ] 6 4 2 – 6 4 2 –
  • D [ C H O ( C O H ) ] > [ C H O H ( C O ) ] 6 4 2 – 6 4 2 –

Q7:

Which is the stronger base, ( C H ) N 3 3 or H B O 2 3 – ? The 𝐾 b of ( C H ) N 3 3 is 6 . 3 Γ— 1 0 βˆ’ 5 and the 𝐾 a of H B O 3 3 is 5 . 4 Γ— 1 0 . βˆ’ 1 0

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