O-Level Combined Science — Chemistry 3

Question 1

What is the number of protons in an atom called?

Accepted Answer

Atomic number

Answer

The atomic number is the number of protons in the nucleus of an atom, and it defines the element.

Question 2

Which property of metals explains why they can be drawn into wires?

Accepted Answer

Ductility

Answer

Ductility is the property that allows metals to be drawn into thin wires without breaking.

Question 3

What type of reaction is: CH₄ + 2O₂ → CO₂ + 2H₂O?

Accepted Answer

Combustion

Answer

This is a combustion reaction — methane (CH₄) burns in oxygen to produce carbon dioxide and water.

Question 4

What is the name of CaCO₃?

Accepted Answer

Calcium carbonate

Answer

CaCO₃ is calcium carbonate, commonly found in limestone, marble, and chalk.

Question 5

Which gas is produced at the cathode during electrolysis of dilute sulfuric acid?

Accepted Answer

Hydrogen

Answer

During electrolysis of dilute sulfuric acid, hydrogen gas is produced at the cathode (negative electrode) as H⁺ ions are reduced.

GCE O-Level Practice Test