Worksheet: Conjugate Acid–Base Pairs

In this worksheet, we will practice identifying conjugate acids and bases in chemical equations and predicting their relative acid or base strengths.

Q1:

In the equation shown, NH3 is the conjugate acid. What is the missing term? NH()+HO+HO323+aq

  • A N H 2 4
  • B N H 4 +
  • C N H 2
  • D N H 3

Q2:

Give the formula and state the symbol of the missing compound in the given equation. HSO()+OH()+HO()32aqaql

  • A S O ( ) 3 2 a q
  • B S O ( ) 2 g
  • C H S O ( ) 2 4 a q
  • D H S O ( ) 2 3 a q
  • E H S ( ) 2 g

Q3:

In the given equation, HPO24 is the conjugate base. What is the missing term? HPO+HO+OH242

  • A H P O 2 3 +
  • B H P O 3 4
  • C H P O 2 4
  • D P O 4 3
  • E H P O 4 2

Q4:

What is the conjugate acid of OH?

  • A H O 2
  • B H O 2 2
  • C H O 3 +
  • D O 2

Q5:

What is the conjugate acid of HO2?

  • A O 2
  • B H O 2 2
  • C H O 3 +
  • D O H

Q6:

What is the conjugate acid of HS?

  • A S 2
  • B S O 2
  • C H S 2

Q7:

In the equation shown, NH3 is the conjugate base. What is the missing term? NH()+HO+OH32aq

  • A N H 3
  • B N H 2 4
  • C N H 2
  • D N H 4 +

Q8:

H S O 2 4 and Cl ions react according to the equation shown. HSO+ClHCl+HSO244

Which species is the Brønsted–Lowry acid in this reaction?

  • A H C l
  • B H S O 2 4
  • C C l
  • D H S O 4

Which species is the conjugate base of the Brønsted–Lowry acid in this reaction?

  • A H S O 4
  • B H S O 2 4
  • C C l
  • D H C l

Which species is the Brønsted–Lowry base in this reaction?

  • A H C l
  • B H S O 2 4
  • C H S O 4
  • D C l

Which species is the conjugate acid of the Brønsted–Lowry base in this reaction?

  • A H C l
  • B H S O 4
  • C H S O 2 4
  • D C l

Q9:

Consider the reaction shown and then answer the following questions. HSO+OHSO+HO4422

Which species is a Brønsted–Lowry acid?

  • A H O 2
  • B S O 4 2
  • C H S O 4
  • D O H

Which species is the conjugate base of a Brønsted–Lowry acid?

  • A H O 2
  • B H S O 4
  • C O H
  • D S O 4 2

Which species is a Brønsted–Lowry base?

  • A H S O 4
  • B H O 2
  • C S O 4 2
  • D O H

Which species is the conjugate acid of a Brønsted–Lowry base?

  • A H S O 4
  • B O H
  • C H O 2
  • D S O 4 2

Q10:

Two aqueous complex ions react according to the equation shown. [Cu(HO)(OH)]+[Al(HO)][Cu(HO)]+[Al(HO)(OH)]25+263+262+252+

Which species is the Brønsted–Lowry acid in this reaction?

  • A [ A l ( H O ) ( O H ) ] 2 5 2 +
  • B [ C u ( H O ) ( O H ) ] 2 5 +
  • C [ A l ( H O ) ] 2 6 3 +
  • D [ C u ( H O ) ] 2 6 2 +

Which species is the conjugate base of the Brønsted–Lowry acid in this reaction?

  • A [ C u ( H O ) ( O H ) ] 2 5 +
  • B [ A l ( H O ) ( O H ) ] 2 5 2 +
  • C [ A l ( H O ) ] 2 6 3 +
  • D [ C u ( H O ) ] 2 6 2 +

Which species is the Brønsted–Lowry base in this reaction?

  • A [ A l ( H O ) ( O H ) ] 2 5 2 +
  • B [ A l ( H O ) ] 2 6 3 +
  • C [ C u ( H O ) ( O H ) ] 2 5 +
  • D [ C u ( H O ) ] 2 6 2 +

Which species is the conjugate acid of the Brønsted–Lowry base in this reaction?

  • A [ A l ( H O ) ( O H ) ] 2 5 2 +
  • B [ C u ( H O ) ( O H ) ] 2 5 +
  • C [ A l ( H O ) ] 2 6 3 +
  • D [ C u ( H O ) ] 2 6 2 +

Q11:

For the reaction of mercury(II) chloride and ammonia, which product is a conjugate Lewis base?

  • A N H 3
  • B H g ( N H ) 3 2
  • C H g C l 2
  • D C l

Q12:

Gastric juice, the digestive fluid produced in the stomach, contains hydrochloric acid, HCl. Milk of magnesia, a suspension of solid Mg(OH)2 in an aqueous medium, is sometimes used to neutralize excess stomach acid. 𝑥HCl()+Mg(OH)()Mg()+2Cl()+2HO()aqaqaqaql22+2

What value of 𝑥 produces a balanced chemical equation?

What is the conjugate acid of Mg(OH)2?

  • A C l
  • B H O 2
  • C H C l
  • D M g 2 +
  • E M g C l 2

Q13:

Why does the complete reaction of a weak acid with a strong base produce a basic solution?

  • AAn excess of strong base must be used for the reaction to reach completion.
  • BThe reaction produces a weak conjugate base and no conjugate acid.
  • CThe reaction produces a strong conjugate base and a weak conjugate acid.
  • DThe reaction produces ions that interact strongly with hydroxide ions in solution, stabilizing their negative charge.
  • EWater competes with the weak acid to react with the base, raising the concentration of hydroxide ions.

Q14:

What is the conjugate base of HN52+?

  • A H N 6 2 2 +
  • B H N 2 2
  • C H N 4 2

Q15:

What is the conjugate acid of HCO3?

  • A C O 2
  • B H C O 2 3
  • C C O 3 2

Q16:

What is the conjugate base of HO22?

  • A H O 3 +
  • B H O 2
  • C H O 2
  • D H O 3 2 +

Q17:

In the shown equation, NH3 is the conjugate base. What is the missing term? NH()+HO+OH32aq

  • A N H 3
  • B N H 2 4
  • C N H 4 +
  • D N H 2

Q18:

What is the conjugate base of HSO4?

  • A H S 2
  • B S O 2
  • C S O 4 2
  • D H S O 2 4

Q19:

Consider the reaction shown. HS+NHHS+NH223

Which species is a Brønsted–Lowry acid?

  • A N H 2
  • B H S 2
  • C H S
  • D N H 3

Which species is the conjugate base of a Brønsted–Lowry acid?

  • A N H 2
  • B H S
  • C H S 2
  • D N H 3

Which species is a Brønsted–Lowry base?

  • A H S 2
  • B N H 3
  • C H S
  • D N H 2

Which species is the conjugate acid of a Brønsted–Lowry base?

  • A N H 2
  • B H S
  • C N H 3
  • D H S 2

Q20:

What is the conjugate acid of NH3?

  • A H O 3 +
  • B N H 4 +
  • C N H 2 2
  • D O H
  • E N H 2

Q21:

What is the conjugate base of OH?

  • A O 2
  • B H O 3 +
  • C H O 2
  • D H +

Q22:

What is the conjugate base of HS?

  • A H S 2
  • B S O 2
  • C S 2

Q23:

In the shown equation, HPO24 is the conjugate acid. What is the missing term? HPO+HO+HO2423+

  • A H P O 2 3 +
  • B H P O 2 4
  • C H P O 3 4
  • D H P O 4 2
  • E P O 4 3

Q24:

What is the conjugate acid of HN52+?

  • A H N 4 2 +
  • B H N 5 2
  • C H N 6 2 +
  • D H N 6 2 2 +
  • E H N 4 2

Q25:

What is the conjugate base of HCO3?

  • A H C O 2 3
  • B C O 3 2
  • C C O 2

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