O-Level Combined Science — Chemistry 2

Question 1

What is the name of the process by which a solid changes directly into a gas?

Accepted Answer

Sublimation

Answer

Sublimation is the process by which a solid changes directly into a gas without passing through the liquid phase, e.g., dry ice (solid CO₂).

Question 2

In electrolysis, where does oxidation occur?

Accepted Answer

At the anode

Answer

Oxidation occurs at the anode (positive electrode). The mnemonic OIL RIG helps: Oxidation Is Loss; Reduction Is Gain.

Question 3

Which element is represented by the symbol 'Na'?

Accepted Answer

Sodium

Answer

'Na' is the chemical symbol for sodium, derived from the Latin word 'Natrium'.

Question 4

What is the empirical formula of a compound with 2 carbon, 6 hydrogen, and 2 oxygen atoms?

Accepted Answer

CH₃O

Answer

Divide all subscripts by the HCF (2): C₂H₆O₂ → CH₃O. The empirical formula is CH₃O.

Question 5

Which gas is used in the Haber Process to make ammonia?

Accepted Answer

Nitrogen and hydrogen

Answer

The Haber Process combines nitrogen (from air) and hydrogen (from natural gas) at high temperature and pressure with an iron catalyst to make ammonia.

GCE O-Level Practice Test

GCE O-Level Practice Test

O-Level Combined Science — Chemistry 2