Question 1a

Marks: 1

a)

Hydrocyanic acid, HCN, is used in the synthesis of polymers and pharmaceuticals. It is a weak acid.

Write an equation to show the dissociation of hydrocyanic acid.

[1]

Key Concepts

Acid & Base Dissociation Constants

Question 1b

Marks: 1

b)

Pyridine is an organic compound with the chemical formula C₅H₅N. It is a weak base.

Write an equation to show how pyridine acts as a base.

[1]

Key Concepts

Acid & Base Dissociation Constants

Question 1c

Marks: 2

c)

Write an equation to show the reaction between hydrocyanic acid and pyridine and identify two conjugate acid-base pairs.

[2]

Key Concepts

Conjugate Acid-Base Pairs

Question 1d

Marks: 2

d)

The pK_a of hydrocyanic acid, HCN, is 9.2 at 298 K. Using section 21 of the Data booklet, deduce which of the two acids, ethanoic, CH₃COOH, or hydrocyanic is the stronger acid.

[2]

Key Concepts

Acid & Base Dissociation Constants

Question 2a

Marks: 4

a)

Using section 21 of the Data booklet, determine theK_a of chloroethanoic acid, dichloroethanoic acid and trichloroethanoic acid and state which is the stronger acid.

[4]

Key Concepts

Acid & Base Dissociation Constants

Question 2b

Marks: 1

b)

Write the K_a expression for dichloroethanoic acid, CHCl₂COOH.

[1]

Key Concepts

Acid & Base Dissociation Constants

Question 2c

Marks: 1

c)

Methylamine, CH₃NH₂, is a substance used to synthesise many commercially available compounds. State the K_b expression for methylamine.

[1]

Key Concepts

Acid & Base Dissociation Constants

Question 2d

Marks: 1

d)

State the relationship between K_aand K_bfor an acid and its conjugate base.

[1]

Key Concepts

Relating Kw to Ka

Question 3a

Marks: 4

a)

A solution of 0.01 mol dm^-3 ethanoic acid has a pH of 3.37 at 298 K. Determine the K_a of ethanoic acid.

[4]

Key Concepts

Acid & Base Calculations

Question 3b

Marks: 5

b)

A solution of 0.10 mol dm^-3methylamine, CH₃NH₂, has a pH of 11.80 at 298 K. Determine the K_b at this temperature.

[5]

Key Concepts

Acid & Base Calculations

Question 3c

Marks: 2

c)

Determine the [H⁺] in a 0.10 mol dm^-3solution whose K_a= 1.00 x 10^-8 at 298 K.

[2]

Key Concepts

Acid & Base Calculations

Question 3d

Marks: 2

d)

Determine the pOH of the solution in part c).

[2]

Key Concepts

Acid & Base Calculations

Question 4a

Marks: 3

a)

Use section 12 of the Data booklet to answer this question.

i)

Write the formula of the conjugate base of methanoic acid.

[1]

ii)

Determine the pK_b of the conjugate base

[2]

Key Concepts

Acid & Base Calculations
Conjugate Acid-Base Pairs

Question 4b

Marks: 1

b)

The pK_aof ethanoic acid is 4.76. Determine whether the conjugate base of methanoic acid is weaker or stronger than the conjugate base of ethanoic acid.

[1]

Key Concepts

Acid & Base Calculations
Conjugate Acid-Base Pairs

Question 4c

Marks: 1

c)

At 283 K the pK_wof pure water is 14.54. Determine the pH at this temperature.

[1]

Key Concepts

Acid & Base Calculations

Question 4d

Marks: 2

d)

Comment on the acid-base nature of water at 283 K in part c).

[2]

Key Concepts

Acid & Base Calculations

DP IB Chemistry: HL

Topic Questions

18.2 Calculations Involving Acids & Bases

Question 1a

Key Concepts

Question 1b

Key Concepts

Question 1c

Key Concepts

Question 1d

Key Concepts

Question 2a

Key Concepts

Question 2b

Key Concepts

Question 2c

Key Concepts

Question 2d

Key Concepts

Question 3a

Key Concepts

Question 3b

Key Concepts

Question 3c

Key Concepts

Question 3d

Key Concepts

Question 4a

Key Concepts

Question 4b

Key Concepts

Question 4c

Key Concepts

Question 4d

Key Concepts

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