Acids, Bases and pH Exam-style MCQs | A-Level Chemistry OCR

Question 1

Which are the Brønsted-Lowry acids in the following equilibrium?

CH₃COOH + C₂H₅COOH ⇌ CH₃COO^- + C₂H₅COOH₂⁺

A

CH₃COOH and C₂H₅COOH

B

CH₃COOH and C₂H₅COOH₂⁺

C

C₂H₅COOH₂⁺ and CH₃COO^-

D

CH₃COO^- and C₂H₅COOH₂⁺

0

/

1

Question 2

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

0

/

1

Question 3

Ammonia reacts with water in a reversible reaction. Which are the Brønsted-Lowry bases?

A

H₂O and OH^-

B

NH₃ and OH^-

C

NH₄⁺ and OH^-

D

NH₄⁺ and NH₃

0

/

1

Question 4

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

0

/

1

Question 5

The equation shows the dissociation of the acid H₃AsO₄in water.

H3AsO₄+ H₂O ⇌ H₂AsO₄^- + H₃O⁺

Which pair is a conjugate acid–base pair?

A

H3AsO₄and H₂O

B

H₂AsO₄^- and H₃O⁺

C

H₃AsO₄ and H₃O⁺

D

H₃O⁺ and H₂O

0

/

1

Question 6

2,4,6-Trichlorophenol is a weak monoprotic acid, with K_a = 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^-3solution 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

0

/

1

Question 7

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

K_w = 1.0 × 10^-14 mol² dm^-6 at 298 K.

A

0.34

B

13.66

C

13.96

D

14.34

0

/

1

Question 8

The acid dissociation constant, K_a, 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

0

/

1

Question 9

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

K_w = 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

0

/

1

Question 10

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

A

-1.82

B

-1.52

C

1.52

D

1.82

0

/

1