Question 1

Which of the following best explains why graphite can conduct electricity, while diamond cannot, even though both are forms of carbon?
Correct answer: Graphite contains delocalized electrons that can move freely between layers.

Accepted Answer

Graphite contains delocalized electrons that can move freely between layers.

Question 2

A student is asked to separate a mixture of sand and salt. Which sequence of experimental techniques should they use to obtain pure salt?
Correct answer: Dissolve in water, filter, evaporate the filtrate.

Accepted Answer

Dissolve in water, filter, evaporate the filtrate.

Question 3

Which of the following statements about isotopes is correct?
Correct answer: Isotopes of an element have the same number of protons but different numbers of neutrons.

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 4

A sample of magnesium reacts completely with hydrochloric acid to produce 2.4 g of magnesium chloride. If the relative atomic masses are Mg = 24, Cl = 35.5, what is the number of moles of magnesium chloride formed?
Correct answer: 0.025 mol

Accepted Answer

0.025 mol

Question 5

Which of the following best describes the process of electrolysis?
Correct answer: The decomposition of a compound using electricity.

Accepted Answer

The decomposition of a compound using electricity.

Question 6

A student is investigating the effect of temperature on the rate of a chemical reaction. Which variable should be kept constant to ensure a fair test?
Correct answer: Concentration of reactants

Accepted Answer

Concentration of reactants

Question 7

Which of the following is a property of ionic compounds?
Correct answer: They conduct electricity when molten or dissolved in water.

Accepted Answer

They conduct electricity when molten or dissolved in water.

Question 8

A chemical reaction is exothermic. Which of the following statements is true?
Correct answer: The products have less energy than the reactants.

Accepted Answer

The products have less energy than the reactants.

Question 9

Which of the following best explains why metals are malleable?
Correct answer: The layers of positive ions can slide over each other while being held together by a sea of delocalized electrons.

Accepted Answer

The layers of positive ions can slide over each other while being held together by a sea of delocalized electrons.

Question 10

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

Accepted Answer

Add silver nitrate; a white precipitate forms.

Question 11

Which of the following best describes the environmental impact of excessive use of fertilizers containing nitrates?
Correct answer: They can cause eutrophication, leading to oxygen depletion in water bodies.

Accepted Answer

They can cause eutrophication, leading to oxygen depletion in water bodies.

Question 12

Which of the following is the correct electronic configuration for a sodium atom (atomic number 11)?
Correct answer: 2,8,1

Accepted Answer

2,8,1

Question 13

A student is asked to calculate the relative molecular mass (Mr) of calcium carbonate (CaCO3). Given Ca = 40, C = 12, O = 16, what is the correct value?
Correct answer: 100

Accepted Answer

100

Question 14

Which of the following best explains why covalent compounds generally have low melting and boiling points?
Correct answer: They have weak intermolecular forces between molecules.

Accepted Answer

They have weak intermolecular forces between molecules.

Question 15

During a laboratory investigation, a student observes that a gas is produced when dilute hydrochloric acid is added to a piece of zinc. Which gas is most likely produced?
Correct answer: Hydrogen

Accepted Answer

Hydrogen

Question 16

Which of the following is a correct statement about the Periodic Table?
Correct answer: Elements in the same group have similar chemical properties.

Accepted Answer

Elements in the same group have similar chemical properties.

Question 17

A solution of sodium hydroxide is titrated with hydrochloric acid. Which indicator would be most suitable for this reaction?
Correct answer: Phenolphthalein

Accepted Answer

Phenolphthalein

Question 18

Which of the following is a correct description of a giant covalent structure?
Correct answer: A structure in which atoms are bonded together in a continuous network by covalent bonds.

Accepted Answer

A structure in which atoms are bonded together in a continuous network by covalent bonds.

Question 19

Which of the following best describes the role of a catalyst in a chemical reaction?
Correct answer: It provides an alternative pathway with lower activation energy.

Accepted Answer

It provides an alternative pathway with lower activation energy.

Question 20

A student is asked to evaluate the safety of an experiment involving concentrated sulfuric acid. Which of the following is the most important safety precaution?
Correct answer: Always add acid to water, not water to acid.

Accepted Answer

Always add acid to water, not water to acid.

Cambridge IGCSE Chemistry 0620: Syllabus Overview and Key Concepts

Study Guide - Practice Questions

Study Guide - Flashcards