Question 1

When magnesium hydroxide dissolves in water, the following equilibrium is established.

Mg(OH)2(s) ⇌ Mg2+(aq) + 2OH-(aq)

The expression for the is solubility product, Ksp

[Mg2+ (aq)​]×2[OH− (aq)​]
[Mg2+ (aq)​]×[OH− (aq)​]2
[Mg(OH)2​ (s)​][Mg2+ (aq)​]×2[OH− (aq)​]​
[Mg(OH)2​ (s)​][Mg2+ (aq)​]×[OH− (aq)​]2​

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Question 2

The solubility product of magnesium hydroxide, Mg(OH)2, is 2.00 × 10-11 mol3 dm-9.

What is the solubility of magnesium hydroxide, in mol dm-3?

  A  

3.16 × 10-6

  B  

4.47 × 10-6

  C  

1.71 × 10-4

  D  

2.71 × 10-4

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Question 3

A solution of hydrochloric acid has pH = 2.

The solution is diluted to one tenth of its original concentration.

What is the pH of the diluted solution?

  A  

0.70

  B  

1.0

  C  

2.7

  D  

3.0

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Question 4

When equimolar amounts of the solutions below are mixed, which forms a buffer solution with a pH less than 7?

  A  

hydrochloric acid and sodium chloride

  B  

ethanoic acid and sodium ethanoate

  C  

sodium hydroxide and sodium chloride

  D  

ammonia and ammonium chloride

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Question 5

The indicator methyl orange is a weak acid and may be represented by the formula HA(aq). The equation for its dissociation is shown below.

HA(aq)        ⇌.       A-        +        H+(aq)

                                                       Colour:        Red                  Yellow

Under certain conditions, at equilibrium, a solution of HA has a yellow colour.

On addition of a small volume of dilute sodium hydroxide, the colour of this solution would

  A  

change from yellow to red

  B  

change from yellow to orange

  C  

change from yellow to orange and then to red

  D  

not change

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Question 6

20 cm3 of 0.10 mol dm-3 hydrochloric acid is added to 10 cm3 of 0.10 mol dm-3 sodium hydroxide.

What is the pH of the resulting mixture?

  A  

1.00

  B  

1.18

  C  

1.30

  D  

1.48

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Question 7

The equation shows the dissociation of the acid H3AsO4 in water.

H3AsO4 + H2O ⇌ H2AsO4- + H3O+

Which pair is a conjugate acid–base pair?

  A  

H3AsO4 and H2O

  B  

H2AsO4- and H3O+

  C  

H3AsO4 and H3O+

  D  

H3O+ and H2O

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Question 8

A buffer solution is prepared by mixing 200 cm3 of 2.00 mol dm-3 propanoic acid, CH3CH2COOH, with 600 cm3 of 1.00 mol dm-3 sodium propanoate, CH3CH2COONa.

Ka for CH3CH2COOH = 1.32 × 10-5 mol dm-3

What is the pH of the buffer solution?

  A  

4.58

  B  

4.70

  C  

5.06

  D  

5.18

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Question 9

2,4,6-Trichlorophenol is a weak monoprotic acid, with Ka = 2.51 × 10-8 mol dm-3 at 298 K.

What is the concentration, in mol dm-3, of hydrogen ions in a 2.00 × 10-3 mol dm-3 solution of 2,4,6-trichlorophenol at 298 K?

  A  

5.02 × 10-11

  B  

7.09 × 10-6

  C  

1.26 × 10-5

  D  

3.54 × 10-3

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Question 10

What is the pH of a 0.46 mol dm-3 solution of potassium hydroxide at 298 K?

Kw = 1.0 × 10-14 mol2 dm-6 at 298 K.

  A  

0.34

  B  

13.66

  C  

13.96

  D  

14.34

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Question 11

The diagram shows a pH curve produced by adding a strong alkali to a weak acid.

Which point on the curve represents a solution that can act as a buffer?

  A  
  B  
  C  
  D  

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Question 12

The acid dissociation constant, Ka, of a weak acid HA has the value 2.56 × 10-4 mol dm-3

What is the pH of a 4.25 × 10-3 mol dm-3 solution of HA?

  A  

5.96

  B  

3.59

  C  

2.98

  D  

2.37

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Question 13

A 0.10 mol dm-3 aqueous solution of an acid is added slowly to 25 cm3 of a 0.10 mol dm-3 aqueous solution of a base.

Which acid–base pair has the highest pH at the equivalence point?

  A  

CH3COOH and NaOH

  B  

CH3COOH and NH3

  C  

HCl and NaOH


  D  

HCl and NH3

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Question 14

Which is the concentration of NaOH(aq), in mol dm-3, that has pH = 14.30?

Kw = 1.00 × 10-14 mol2 dm-6 at 25°C

  A  

-1.16

  B  

5.01 × 10-15

  C  

2.00 × 1014

  D  

2.00

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Question 15

What is the pH of 0.015 mol dm-3 sulfuric acid?

  A  

-1.82

  B  

-1.52

  C  

1.52

  D  

1.82

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