Question 1

A student is asked to separate a mixture of sand, salt, and iron filings. Which sequence of experimental techniques would best achieve complete separation of all three components?
Correct answer: Use a magnet to remove iron filings, dissolve the mixture in water, filter to separate sand, then evaporate the water to recover salt.

Accepted Answer

Use a magnet to remove iron filings, dissolve the mixture in water, filter to separate sand, then evaporate the water to recover salt.

Question 2

Which of the following best explains why ionic compounds generally have high melting points?
Correct answer: They have strong electrostatic forces of attraction between oppositely charged ions.

Accepted Answer

They have strong electrostatic forces of attraction between oppositely charged ions.

Question 3

A chemical plant releases sulfur dioxide (SO₂) into the atmosphere. Which environmental problem is most directly caused by this emission, and what is a likely consequence?
Correct answer: Acid rain; damage to aquatic life and buildings.

Accepted Answer

Acid rain; damage to aquatic life and buildings.

Question 4

Which of the following statements about the Periodic Table is correct?
Correct answer: Elements in the same group have similar chemical properties due to the same number of outer electrons.

Accepted Answer

Elements in the same group have similar chemical properties due to the same number of outer electrons.

Question 5

A student is titrating hydrochloric acid (HCl) with sodium hydroxide (NaOH). Which indicator would be most appropriate for this reaction, and why?
Correct answer: Phenolphthalein, because it changes color in the pH range of a strong acid-strong base titration.

Accepted Answer

Phenolphthalein, because it changes color in the pH range of a strong acid-strong base titration.

Question 6

Which of the following best describes the process of electrolysis of molten sodium chloride (NaCl)?
Correct answer: Sodium ions are reduced at the cathode and chlorine ions are oxidized at the anode.

Accepted Answer

Sodium ions are reduced at the cathode and chlorine ions are oxidized at the anode.

Question 7

A sample of calcium carbonate (CaCO₃) is heated strongly. Which products are formed, and what type of reaction is this?
Correct answer: Calcium oxide and carbon dioxide; decomposition reaction.

Accepted Answer

Calcium oxide and carbon dioxide; decomposition reaction.

Question 8

Which of the following is a correct statement about exothermic and endothermic reactions?
Correct answer: Exothermic reactions release heat to the surroundings, causing a temperature increase.

Accepted Answer

Exothermic reactions release heat to the surroundings, causing a temperature increase.

Question 9

A student is given a colorless solution and asked to identify the presence of sulfate ions. Which reagent should be added, and what observation would confirm the presence of sulfate ions?
Correct answer: Add barium chloride solution; a white precipitate forms.

Accepted Answer

Add barium chloride solution; a white precipitate forms.

Question 10

Which of the following best explains why metals are good conductors of electricity?
Correct answer: They have free-moving delocalized electrons that carry charge.

Accepted Answer

They have free-moving delocalized electrons that carry charge.

Question 11

A 0.25 mol sample of methane (CH₄) is completely combusted in oxygen. What is the total number of moles of carbon dioxide produced?
Correct answer: 0.25 mol

Accepted Answer

0.25 mol

Question 12

Which of the following is a correct safety precaution when heating a substance in a test tube during a laboratory experiment?
Correct answer: Point the mouth of the test tube away from yourself and others.

Accepted Answer

Point the mouth of the test tube away from yourself and others.

Question 13

Which of the following best describes the role of a catalyst in a chemical reaction?
Correct answer: It lowers the activation energy, increasing the rate of reaction without being consumed.

Accepted Answer

It lowers the activation energy, increasing the rate of reaction without being consumed.

Question 14

A student is asked to calculate the empirical formula of a compound containing 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula?
Correct answer: CH₂O

Accepted Answer

CH₂O

Question 15

Which of the following is a correct statement about acids, bases, and salts?
Correct answer: A salt is formed when an acid reacts with a base, producing water and a salt.

Accepted Answer

A salt is formed when an acid reacts with a base, producing water and a salt.

Question 16

Which of the following best describes the greenhouse effect and its connection to chemistry?
Correct answer: Certain gases, such as carbon dioxide, trap heat in the Earth's atmosphere, leading to global warming.

Accepted Answer

Certain gases, such as carbon dioxide, trap heat in the Earth's atmosphere, leading to global warming.

Question 17

Which of the following is the correct order of reactivity for the metals magnesium, copper, potassium, and iron (from most to least reactive)?
Correct answer: Potassium \u003e Magnesium \u003e Iron \u003e Copper

Accepted Answer

Potassium \u003e Magnesium \u003e Iron \u003e Copper

Question 18

A student is analyzing a sample using flame tests. Which color would indicate the presence of sodium ions?
Correct answer: Yellow

Accepted Answer

Yellow

Question 19

Which of the following best describes the difference between a compound and a mixture?
Correct answer: A compound has a fixed composition and chemical bonds between elements, while a mixture has variable composition and no chemical bonds between components.

Accepted Answer

A compound has a fixed composition and chemical bonds between elements, while a mixture has variable composition and no chemical bonds between components.

Question 20

Which of the following best explains why water is considered a universal solvent in chemistry?
Correct answer: It dissolves many ionic and polar substances due to its polarity.

Accepted Answer

It dissolves many ionic and polar substances due to its polarity.

Overview of Cambridge IGCSE Chemistry 0620 Syllabus

Study Guide - Practice Questions

Study Guide - Flashcards