National 5 Chemistry Unit 1 Acids and Alkalis Past Paper ..., Exams of Chemistry

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National 5 Chemistry

Unit 1

Acids and Alkalis

Past Paper Questions

1. Which of the following oxides, when shaken with water, would leave the pH unchanged? A. Carbon dioxide B. Copper oxide C. Sodium oxide D. Sulphur dioxide
2. Which compound would not neutralise hydrochloric acid? A. Sodium carbonate B. Sodium chloride C. Sodium oxide D. Sodium hydroxide
3. In which of the following test tubes will a gas be produced?
4. An acidic solution contains A. Only hydrogen ions B. Only hydroxide ions C. More hydrogen ions than hydroxide ions D. More hydroxide ions than hydrogen ions
5. Which of the following oxides, when shaken with water, would give an alkaline solution? A. Calcium oxide B. Nickel oxide C. Nitrogen dioxide D. Sulphur dioxide

11. A student carried out an experiment to prepare the salt, magnesium sulphate. Part of the student’s experiment assessment sheet is shown.

a. Name the acid used to make this salt. (1) b. How would the student know when to stop adding magnesium in Step 1? (1) c. Why was the reaction mixture filtered in Step 2? (1)

12. An oxide is a compound that contains at least one oxygen atom and only one other element in its chemical formula. Using your knowledge of chemistry, comment on the chemistry of oxides. (3)
13. Water is one of the most versatile of all chemicals and features in many chemical reactions and processes. Using your knowledge of chemistry, comment on the chemistry of water. (3)
14. Sulfur dioxide is an important industrial chemical. Sulfur dioxide dissolves in water to produce sulfurous acid.

SO 2 (g) + H 2 O(ℓ)  H 2 SO 3 (aq)

a. Explain the change in the pH of the solution as sulfur dioxide dissolves. (2) b. The graph shows the solubility of sulfur dioxide at different temperatures.

Describe the general trend in solubility as the temperature of the water increases. (1)

15. Some sources of methane gas contain hydrogen sulfide, H 2 S. If hydrogen sulfide is not removed before methane gas is burned, sulfur dioxide is formed. When sulfur dioxide dissolves in water in the atmosphere, acid rain is produced.

a. Copy and complete the sentences, choosing the correct words.

Acid rain contains more ( hydrogen/hydroxide ) ions than ( hydrogen/hydroxide ) ions. (1)

b. In industry, calcium oxide is reacted with sulfur dioxide to reduce the volume of sulfur dioxide released into the atmosphere. Explain why calcium oxide is able to reduce the volume of sulfur dioxide gas released. (2)

16. Sulfur dioxide gas is produced when fossil fuels containing sulfur are burned. When sulfur dioxide dissolves in water in the atmosphere “acid rain” is produced.

a. Copy and complete the sentences, choosing the correct words.

Compared with pure water, acid rain contains a ( higher/a lower/the same ) concentration of hydrogen ions. (1)

17. A student investigated the reaction of carbonates with dilute hydrochloric acid. In one reaction lithium carbonate reacted with dilute hydrochloric acid. The equation for the reaction is:

Li 2 CO 3 (s) + HCl(aq) → LiCl(aq) + CO 2 (g) + H 2 O(l)

a. Balance this equation. (1) b. Identify the salt produced in this reaction. (1)

18. Antacid tablets are used to treat indigestion which is caused by excess acid in the stomach. Different brands of tablets contain different active ingredients.

a. Complete the table to show the cost of using magnesium carbonate to neutralise 20 cm^3 of acid. (1) b. Which one of the four active ingredients would you use to neutralise excess stomach acid? Explain your choice. (1)

19. In a reaction, nitric acid is converted to potassium nitrate. The equation for the reaction taking place is

HNO 3 (aq) + KOH(aq)  KNO 3 (aq) + H 2 O(ℓ)

a. Name the type of chemical reaction taking place in stage 3. (1) b. State how a sample of solid potassium nitrate could be obtained from the potassium nitrate solution. (1)