O-Level Combined Science — Chemistry 4

Question 1

What type of isomerism do butane and methylpropane exhibit?

Accepted Answer

Structural isomerism

Answer

Butane (CH₃CH₂CH₂CH₃) and methylpropane ((CH₃)₂CHCH₃) are structural isomers — same molecular formula (C₄H₁₀), different arrangements.

Question 2

Which type of chemical bond is formed when electrons are transferred from one atom to another?

Accepted Answer

Ionic bond

Answer

Ionic bonds are formed by the transfer of electrons from a metal atom to a non-metal atom, creating oppositely charged ions.

Question 3

What is the test for carbon dioxide gas?

Accepted Answer

Turns limewater milky

Answer

Carbon dioxide turns limewater (calcium hydroxide solution) milky/cloudy due to the formation of calcium carbonate precipitate.

Question 4

In the periodic table, elements in the same group have the same number of:

Accepted Answer

Electrons in the outer shell

Answer

Elements in the same group have the same number of electrons in their outermost shell, giving them similar chemical properties.

Question 5

What is produced when ethanol reacts with ethanoic acid?

Accepted Answer

Ethyl ethanoate and water

Answer

Esterification: ethanol + ethanoic acid → ethyl ethanoate (an ester) + water, in the presence of a concentrated acid catalyst.

GCE O-Level Practice Test