8.6 Past Paper Questions

1. An aqueous solution of which of the following reacts with Magnesium metal?

A. Ammonia

B. Hydrogen Chloride

C. Potassium Hydroxide

D. Sodium Hydrogencarbonate

2. Which of the following is/are formed when a metal oxide reacts with a dilute acid?

I. A metal salt

II. Water

III. Hydrogen gas

A. I only B. I and II only

C. II and III only D. I, II and III

3. Four aqueous solutions, I, II, III and IV, are listed below.

I. 0.100 mol dm^–3 HCl

II. 0.010 mol dm^–3 HCl

III. 0.100 mol dm^–3 NaOH

IV. 0.010 mol dm^–3 NaOH

What is the correct order of increasing pH of these solutions?

A. I, II, III, IV

B. I, II, IV, III

C. II, I, III, IV

D. II, I, IV, III

4. Which substance can be dissolved in water to give a 0.1 mol dm^–3solution with a high pH and a high electrical conductivity?

A. HCl

B. NaCl

C. NH₃

D. NaOH

5. The pH of a solution is 2. If it increases to 6, how many times greater is the [H⁺] ?

A. 3

B. 4

C. 1000

D. 10 000

6. The pH of solution X is 1 and that of Y is 2. Which statement is correct about the hydrogen ion concentrations in the two solutions?

A. [H⁺] in X is half that in Y.

B. [H⁺] in X is twice that in Y.

C. [H⁺] in X is one tenth of that in Y.

D. [H⁺] in X is ten times that in Y.

7. Lime was added to a sample of soil and the pH changed from 4 to 6. What was the corresponding change in the hydrogen ion concentration?

A. increased by a factor of 2

B. increased by a factor of 100

C. decreased by a factor of 2

D. decreased by a factor of 100

8. When the following 1.0 mol dm^–3 solutions are listed in increasing order of pH (lowest first), what is the correct order?

A. HNO₃ < H₂CO₃ < NH₃ < Ba(OH)₂

B. NH₃ < Ba(OH)₂ < H₂CO₃ < HNO₃

C. Ba(OH)₂ < H₂CO₃ < NH₃ < HNO₃

D. HNO₃ < H₂CO₃ < Ba(OH)₂ < NH₃

9. Which change in [H⁺] causes the biggest increase in pH?

A. A change in [[H⁺] _(aq)] from 1×10–3 to 1×10–2 mol dm^–3

B. A change in [[H⁺] _(aq)] from 1×10–3 to 1×10–4 mol dm^–3

C. A change in [[H⁺] _(aq)] from 1×10–4 to 1×10–2 mol dm^–3

D. A change in [[H⁺] _(aq)] from 1×10–4 to 1×10–6 mol dm^–3

10. Which methods can distinguish between solutions of a strong monoprotic acid and a weak monoprotic acid of the same concentration?

I. Add magnesium to each & measure the rate of the formation of gas bubbles.

II. Add aqueous Sodium Hydroxide to each solution and measure the temperature change.

III. Use solutions in circuits with batteries & lamps & see lamp brightness

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

11. Which species are a conjugate pair according to the Brønsted-Lowry theory?

A. CH₃COOH and CH₃CHO

B. NH₃ and BF₃

C. H₂NO₃⁺ and NO₃^–

D. H₂SO₄ and HSO₄^–

12. Which is not a strong acid?

A. Nitric acid B. Sulphuric acid

C. Carbonic acid D. Hydrochloric acid

13. Lime is added to a lake to neutralize the effects of acid rain. The pH value of the lake water rises from 4 to 7. What is the change in concentration of H⁺ ions in the lake water?

A. An increase by a factor of 3

B. An increase by a factor of 1000

C. A decrease by a factor of 3

D. A decrease by a factor of 1000

14. Which is a Brønsted-Lowry acid-base pair?

A. H₂O and O^2–

B. CH₃COOH and CH₃COO^–

C. NH₄⁺ and NH^2–

D. H₂SO₄ and SO₄^2–

15. Solutions of Hydrochloric Acid (HCl_(aq)) and Ethanoic Acid (CH₃COOH_(aq)) of the same concentration reacted completely with 5.0 g of Calcium Carbonate in separate containers. Which statement is correct?

A. CH₃COOH_(aq) reacted slower because it has a lower pH than HCl_(aq).

B. A smaller volume of CO_2(g) was produced with CH₃COOH_(aq) than with HCl_(aq)

C. A greater volume of CO_2(g) was produced with CH₃COOH_(aq) than with HCl_(aq)

D. The same volume of CO_2(g) was produced with both CH₃COOH_(aq) and HCl_(aq)

16. Solutions of hydrochloric acid (HCl(aq)) and ethanoic acid (CH3COOH(aq)) of the same concentration reacted completely with 5.0 g of calcium carbonate in separate containers. Which statement is correct?

A. CH3COOH(aq) reacted slower because it has a lower pH than HCl(aq).

B. A smaller volume of CO2(g) was produced with CH3COOH(aq) than with HCl(aq).

C. A greater volume of CO2(g) was produced with CH3COOH(aq) than with HCl(aq).

D. The same volume of CO2(g) was produced with both CH3COOH(aq) and HCl(aq).

17. Which acids are strong?

I. HCl_(aq)

II. HNO_3(aq)

III. H₂SO_4(aq)

A. I and II only B. I and III only

C. II and III only D. I, II and III

18. The pH of a solution changes from pH = 1 to pH = 3. What happens to the [H⁺] during this pH change?

A. It increases by a factor of 100.

B. It decreases by a factor of 100.

C. It increases by a factor of 1000.

D. It decreases by a factor of 1000.

19. What is the conjugate base of the HSO₄^–_(aq) ion?

A. H₂SO_4(aq)

B. SO₄^2–_(aq)

C. H₂O_(l)

D. H₃O⁺_(aq)

21. Which substance, when dissolved in water, to give a 0.1 mol dm^–3solution, has the highest pH?

A. HCl

B. NaCl

C. NH₃

D. NaOH

22. Which methods will distinguish between equimolar solutions of a strong base and a strong acid?

I. Add magnesium to each solution and look for the formation of gas bubbles.

II. Add aqueous sodium hydroxide to each solution and measure the temperature change.

III. Use each solution in a circuit with a battery and lamp and see how bright the lamp glows.

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

23. (a) Aqueous XO₄^3– ions form a precipitate with aqueous silver ions, Ag⁺. Write a balanced equation for the reaction, including state symbols.

................................................................................................................................(2)

(b) When 41.18 cm³ of a solution of aqueous silver ions with a concentration of 0.2040 mol dm^–3 is added to a solution of XO₄^3– ions, 1.172 g of the precipitate is formed.

(i) Calculate the amount (in moles) of Ag⁺ ions used in the reaction.

......................................................................................................................(1)

(ii) Calculate the amount (in moles) of the precipitate formed.

......................................................................................................................(1)

(iii) Calculate the molar mass of the precipitate.

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......................................................................................................................(2)

(iv) Determine the relative atomic mass of X and identify the element.

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......................................................................................................................(2)

(Total 8 marks)

24. (a) (i) A solution of Hydrochloric Acid has a concentration of 0.10 mol dm^–3 and a pH value of 1. The solution is diluted by a factor of 100. Determine the concentration of the acid and the pH value in the diluted solution.

..........................................................................................................................

......................................................................................................................(2)

(ii) Explain why 0.10 mol dm^–3 Ethanoic Acid solution and the diluted solution in (a) (i) have similar [H⁺] values.

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......................................................................................................................(3)

(b) Suggest one method, other than measuring pH, which could be used to distinguish between solutions of a strong acid and a weak acid of the same concentration. State the expected results.

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(2)

(Total 7 marks)

25. Define the terms strong acid and weak acid. Using Hydrochloric and Ethanoic Acid as examples, write equations to show the dissociation of each acid in aqueous solution.

……………………………………………………………………………………………

(Total 4 marks)

26. (i) Calcium Carbonate is added to separate solutions of Hydrochloric acid and Ethanoic Acid of the same concentration. State one similarity and one difference in the observations you could make.

………………………………………………………………………………………

(2)

(ii) Write an equation for the reaction between Hydrochloric Acid and Calcium Carbonate.

………………………………………………………………………………………

(2)

(iii) Determine the volume of 1.50 mol dm^–3 Hydrochloric Acid that would react with exactly 1.25 g of Calcium Carbonate.

………………………………………………………………………………………

……………………………………………………………………………………….

(3)

(iv) Calculate the volume of carbon dioxide, measured at 273 K and 1.01×10⁵ Pa, which would be produced when 1.25 g of Calcium Carbonate reacts completely with the Hydrochloric Acid.

………………………………………………………………………………………

(2)

(Total 9 marks)

27. The pH values of solutions of three organic acids of the same concentration were measured.

acid X pH = 5

acid Y pH = 2

acid Z pH = 3

(i) Identify which solution is the least acidic. (1)

(ii) Deduce how the [H⁺] values compare in solutions of acids Y and Z. (2)

(iii) Arrange the solutions of the 3 acids in decreasing order of electrical conductivity, starting with the greatest conductivity, giving a reason for your choice. (2)

(Total 5 marks)

28. The equilibrium reached when Ethanoic Acid is added to water is by the equation:

CH₃COOH_(l) + H₂O_(l) ⇌ CH₃COO^–_(aq)+H₃O⁺_(aq)

Define the terms Brønsted-Lowry acid and Lewis base, and identify two examples of each of these species in the equation.

(Total 4 marks)

29. Identify one example of a strong acid and one example of a weak acid. Outline three different methods to distinguish between equimolar solutions of these acids in the laboratory. State how the results would differ for each acid.

(Total 5 marks)

30. Vinegar has a pH of approximately 3 and some detergents have a pH of approximately 8. State and explain which of these has the higher concentration of H⁺ and by what factor.

(Total 1 mark)

31. Define the terms Brønsted-Lowry acid and Lewis acid. For each type of acid, identify one example other than water and write an equation to illustrate the definition.

(Total 5 marks)

32. The pH values of three acidic solutions, X, Y and Z, are shown in the following table:

(i) Solutions X and Z have the same acid concentration. Explain, by reference to both acids, why they have different pH values. (2)

(ii) Deduce by what factor the values of [H⁺] in solutions X and Y differ. (1)

(Total 3 marks)

33. State and explain two methods, other than measuring pH, which could be used to distinguish between 1.0 mol dm^–3 solutions of Nitric Acid and Ethanoic Acid.

(Total 4 marks)

34. Propanoic Acid is classified as a weak acid.

(a) State the meaning of the term weak acid.

....................................................................................................................................

(1)

(b) State, giving a reason in each case, two methods other than measuring pH, that can distinguish between 0.100 mol dm^–3Propanoic Acid and 0.100 mol dm^–3 Nitric Acid.

....................................................................................................................................

(2)

(Total 3 marks)

35. State an equation for the reaction of Propanoic Acid with water. Identify one conjugate Brønsted-Lowry pair.

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(Total 2 marks)