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Acids, bases and titration — Question 5

QCAA 2023, Paper 2 · 13 marks

Q5 · 2023 · Paper 2Unclassified13 marks

QUESTION 5 (13 marks)

The table gives the properties of four monoprotic acids.

Acid

Concentration (mol L-1)
[H +] (mol L-1)

pH

Ka

1

0.200

7.90 × 10-5

2

0.100

4.20 × 10-3

2.34

1.80 × 10-4
CH3COOH(aq)

0.100

1.78 × 10-5

HCl(aq)

0.010

1.00 × 10-2

2.00

>1

(a) Determine the relative strength of acids 1 and 2 by contrasting their Ka values.

[3 marks]

(b) Write a balanced chemical equation for the dissociation of ethanoic acid (CH3COOH) in water.

[2 marks]

(c) Identify whether the conjugate base of ethanoic acid (CH3COOH(aq)) is amphiprotic. Explain your reasoning.

[2 marks]

(d) Calculate the pH of the aqueous solution of ethanoic acid (CH3COOH). Show your working.

[3 marks]

(e) Determine the volume of water that would need to be added to 100.0 mL of HCl(aq) to change the pH from 2.00 to 3.00. Explain your reasoning.

[3 marks]

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