Question 1

A sealed syringe contains 20.0 mL of oxygen gas at 25°C and 1.00 atm. If the syringe is placed in an ice bath at 0°C while keeping the pressure constant, what will be the new volume of the gas? (Assume ideal gas behavior.)
Correct answer: 18.3 mL

Accepted Answer

18.3 mL

Question 2

Which of the following best explains why graphite conducts electricity but diamond does not, even though both are forms of carbon?
Correct answer: Graphite has delocalized electrons that can move between layers, while diamond's electrons are all involved in covalent bonds.

Accepted Answer

Graphite has delocalized electrons that can move between layers, while diamond's electrons are all involved in covalent bonds.

Question 3

A sample of chlorine contains two isotopes: 75% 35Cl (atomic mass = 34.97 u) and 25% 37Cl (atomic mass = 36.97 u). What is the relative atomic mass of chlorine in this sample?
Correct answer: 35.47 u

Accepted Answer

35.47 u

Question 4

Which of the following statements about ionic and covalent compounds is correct?
Correct answer: Ionic compounds conduct electricity when molten, while covalent compounds generally do not conduct electricity.

Accepted Answer

Ionic compounds conduct electricity when molten, while covalent compounds generally do not conduct electricity.

Question 5

A student is asked to design an experiment to compare the reactivity of three metals: magnesium, zinc, and copper, with dilute hydrochloric acid. Which of the following is the best method to ensure a fair test?
Correct answer: Use equal masses of each metal and the same volume and concentration of acid for each test.

Accepted Answer

Use equal masses of each metal and the same volume and concentration of acid for each test.

Question 6

Which of the following best describes the role of a salt bridge in an electrochemical cell?
Correct answer: It allows the movement of ions to maintain electrical neutrality between the two half-cells.

Accepted Answer

It allows the movement of ions to maintain electrical neutrality between the two half-cells.

Question 7

Which of the following is a correct electron configuration for a neutral atom of sulfur (atomic number 16)?
Correct answer: 1s² 2s² 2p⁶ 3s² 3p⁴

Accepted Answer

1s² 2s² 2p⁶ 3s² 3p⁴

Question 8

A 2.00 g sample of magnesium reacts completely with excess hydrochloric acid. How many liters of hydrogen gas (at STP) are produced? (Mg + 2HCl → MgCl₂ + H₂; molar mass of Mg = 24.3 g/mol; 1 mol gas at STP = 22.4 L)
Correct answer: 1.85 L

Accepted Answer

1.85 L

Question 9

Which of the following best explains why increasing the temperature increases the rate of a chemical reaction?
Correct answer: Particles have more kinetic energy, so more collisions have enough energy to overcome the activation energy barrier.

Accepted Answer

Particles have more kinetic energy, so more collisions have enough energy to overcome the activation energy barrier.

Question 10

Which of the following is a correct statement about acids and bases according to the Brønsted-Lowry theory?
Correct answer: An acid is a proton donor and a base is a proton acceptor.

Accepted Answer

An acid is a proton donor and a base is a proton acceptor.

Question 11

A student is asked to determine the purity of a sample of sodium carbonate (Na₂CO₃) by titration with hydrochloric acid. Which of the following best describes the experimental approach?
Correct answer: Dissolve a known mass of the sample in water, titrate with standard HCl, and compare the amount of acid required to the theoretical value for pure Na₂CO₃.

Accepted Answer

Dissolve a known mass of the sample in water, titrate with standard HCl, and compare the amount of acid required to the theoretical value for pure Na₂CO₃.

Question 12

Which of the following environmental issues is most directly related to the release of sulfur dioxide (SO₂) from burning fossil fuels?
Correct answer: Acid rain

Accepted Answer

Acid rain

Question 13

Which of the following best describes the trend in atomic radius across Period 3 of the Periodic Table (from sodium to argon)?
Correct answer: Atomic radius decreases from sodium to argon.

Accepted Answer

Atomic radius decreases from sodium to argon.

Question 14

A student is asked to explain why metals are malleable and conduct electricity. Which of the following is the best explanation?
Correct answer: Metals have a lattice of positive ions surrounded by a sea of delocalized electrons that can move and allow layers to slide over each other.

Accepted Answer

Metals have a lattice of positive ions surrounded by a sea of delocalized electrons that can move and allow layers to slide over each other.

Question 15

Which of the following is the best example of a giant covalent structure?
Correct answer: Diamond

Accepted Answer

Diamond

Question 16

A balloon filled with helium gas has a volume of 2.00 L at 1.00 atm and 300 K. If the balloon rises to a higher altitude where the pressure is 0.80 atm and the temperature is 270 K, what is the new volume of the balloon? (Assume ideal gas behavior.)
Correct answer: 2.78 L

Accepted Answer

2.78 L

Question 17

Which of the following is a correct statement about the use of scientific data in chemistry?
Correct answer: Data should be analyzed using appropriate units and significant figures, and conclusions should be based on evidence.

Accepted Answer

Data should be analyzed using appropriate units and significant figures, and conclusions should be based on evidence.

Question 18

Which of the following best describes a safe laboratory practice when heating a substance in a test tube?
Correct answer: Point the open end of the test tube away from yourself and others.

Accepted Answer

Point the open end of the test tube away from yourself and others.

Question 19

Which of the following is the best example of a redox reaction?
Correct answer: Zinc metal reacting with copper(II) sulfate to produce zinc sulfate and copper metal.

Accepted Answer

Zinc metal reacting with copper(II) sulfate to produce zinc sulfate and copper metal.

Question 20

Which of the following is a correct statement about organic chemistry?
Correct answer: Organic chemistry is the study of carbon-containing compounds, typically with covalent bonding.

Accepted Answer

Organic chemistry is the study of carbon-containing compounds, typically with covalent bonding.

Overview of Cambridge IGCSE Chemistry 0620 Syllabus

Study Guide - Practice Questions

Study Guide - Flashcards