CIE iGCSE Co-Ordinated Science C7.3 Preparation of salts Exam Style Questions Paper 1
Question
What is the chemical name for lime?
A. calcium carbonate
B. calcium hydroxide
C. calcium oxide
D. calcium sulfate
▶️Answer/Explanation
Answer: C
Explanation: Lime is the common name for calcium oxide (CaO). It is produced by heating limestone (calcium carbonate) in a process called calcination.
Question
Which compound is used to neutralise acidic gases?
A) calcium carbonate
B) calcium chloride
C) calcium phosphate
D) calcium sulfate
▶️Answer/Explanation
Answer: A) calcium carbonate
Explanation: Calcium carbonate is commonly used to neutralize acidic gases, such as sulfur dioxide, in processes like flue gas desulfurization.
Question
Magnesium chloride is prepared by reacting an excess of insoluble magnesium oxide with dilute
hydrochloric acid.
Which processes are used to obtain pure crystals of magnesium chloride from the reaction
mixture?
1 distillation
2 evaporation
3 filtration
(A) 1 followed by 2
(B) 3 followed by 2
(C) 3 followed by 1
(D) 1 followed by 3, followed by 2
▶️Answer/Explanation
Ans : B
Question
Which word equation describes the manufacture of lime from limestone?
(A) calcium carbonate → calcium hydroxide + carbon dioxide
(B) calcium carbonate → calcium oxide + carbon dioxide
(C) calcium hydroxide → calcium oxide + water
(D) calcium oxide + carbon dioxide → calcium carbonate
▶️Answer/Explanation
Ans: B
Question
Solid S is added to dilute hydrochloric acid in the apparatus shown.
▶️Answer/Explanation
Ans: B
Question
Salts are made when four substances react separately with dilute hydrochloric acid.
1. magnesium
2. magnesium carbonate
3. magnesium hydroxide
4. magnesium oxide
Which substances produce a gas when reacted with dilute hydrochloric acid?
(A) 1 and 2 (B) 1 and 3 (C) 2 and 4 (D) 3 and 4
▶️Answer/Explanation
Ans: A
Question
Substance X is insoluble in water.
It reacts with dilute nitric acid to produce solution Y and a gas which turns limewater milky.
A white precipitate is formed when aqueous sodium hydroxide is added to solution Y. This precipitate remains when excess sodium hydroxide is added.
What is substance X?
A calcium carbonate
B calcium chloride
C zinc carbonate
D zinc chloride
▶️Answer/Explanation
Answer: A calcium carbonate
Explanation: Calcium carbonate (CaCO₃) is insoluble in water and reacts with dilute nitric acid to produce calcium nitrate (solution Y) and carbon dioxide gas, which turns limewater milky. When aqueous sodium hydroxide is added to solution Y, a white precipitate of calcium hydroxide forms, which remains even when excess sodium hydroxide is added.
Question
Salts are made by reacting dilute hydrochloric acid with four substances. Which substances produce a gas when reacted with dilute hydrochloric acid?
- magnesium
- magnesium carbonate
- magnesium hydroxide
- magnesium oxide
A. 1 and 2
B. 1 and 3
C. 2 and 4
D. 3 and 4
▶️Answer/Explanation
Answer: A. 1 and 2
Explanation: Magnesium (1) reacts with hydrochloric acid to produce hydrogen gas, and magnesium carbonate (2) reacts with hydrochloric acid to produce carbon dioxide gas. Magnesium hydroxide (3) and magnesium oxide (4) do not produce a gas when reacting with hydrochloric acid.
Question
Copper sulfate is made by adding an excess of copper carbonate to dilute sulfuric acid and stirring. The excess solid is removed. Most of the water is then removed. The solution is left for solid copper sulfate to form. In which order is apparatus used?
A. Bunsen burner, tripod and flask → filter funnel → crystallising dish
B. Bunsen burner, tripod and flask → crystallising dish → filter funnel
C. filter funnel → crystallising dish → Bunsen burner, tripod and flask
D. filter funnel → Bunsen burner, tripod and flask → crystallising dish
▶️Answer/Explanation
Answer: D. filter funnel → Bunsen burner, tripod and flask → crystallising dish
Explanation: First, the mixture is filtered to remove excess copper carbonate. Then, the solution is heated to remove most of the water. Finally, the solution is left in a crystallising dish to allow copper sulfate crystals to form.
Question
Zinc oxide is an insoluble base. It reacts with dilute hydrochloric acid to produce zinc chloride. Zinc chloride is soluble in water. Which statement about the preparation of zinc chloride crystals is correct?
A. Once the reaction is complete there is no need to filter the reaction mixture.
B. The reaction mixture is neutral at the point that no more zinc oxide reacts.
C. Zinc chloride crystals are obtained by evaporation to dryness.
D. Zinc chloride precipitates when the solution becomes neutral.
▶️Answer/Explanation
Answer: B
Explanation: Zinc oxide reacts with hydrochloric acid to form zinc chloride and water. When all the zinc oxide has reacted, the solution becomes neutral. The zinc chloride can then be crystallized by evaporating the water, but it does not precipitate when the solution becomes neutral.
Question
Which statement about calcium carbonate is not correct?
A) It forms carbon dioxide when it is heated.
B) It forms carbon dioxide when it is mixed with dilute hydrochloric acid.
C) It is formed by heating lime.
D) It neutralises acids.
▶️Answer/Explanation
Answer: C) It is formed by heating lime.
Explanation: Calcium carbonate (CaCO₃) decomposes to form calcium oxide (lime) and carbon dioxide when heated, not the other way around. It does neutralize acids and releases CO₂ when reacted with dilute hydrochloric acid.
Question
Hydrochloric acid and sodium hydroxide neutralize each other to form water and sodium chloride. Which method is used to make the solution crystallize?
A. chromatography
B. evaporation
C. filtration
D. fractional distillation
▶️Answer/Explanation
Answer: B
Explanation: Evaporation is used to crystallize the salt from the solution. As the water evaporates, the concentration of sodium chloride increases until it crystallizes out of the solution.
Question
Hydrochloric acid and sodium hydroxide neutralise each other to form water and sodium chloride.
Which method is used to make the solution crystallise?
A. chromatography
B. evaporation
C. filtration
D. fractional distillation
▶️Answer/Explanation
Answer: B
Explanation: Evaporation is used to crystallise sodium chloride from the solution. As the water evaporates, the sodium chloride forms crystals.