Syllabus and sample questions

Questions will generally be based on the syllabus of the GCE Ordinary Level. The committee strives to produce high-level questions and therefore, the questions may not carry the same style as the O levels examination. Some content knowledge is essential, but the focus of the questions is on analytical, reasoning and creative skills.

You may refer to the below past year questions provided by the scientific committee.

Round 1: Sample question

Download past year questions here.

Round 2: Sample question

 Watch the Carrot Chemistry video and answer the Questions below.

Question 1

Why do you think the reaction should be performed in water and not organic solvents? [2m]

Answer: Reaction depends on the activity of an enzyme found in carrots, which will get degraded/ destroyed/ denatured/ inactivated (any synonym) in organic solvent.

Question 2

Why should the reaction not be heated? [2m]

Answer: Carrot enzyme will be degraded/ destroyed/ denatured/ inactivated (any synonym) by heat. When the enzyme is no longer active, it cannot catalyse/ take part in the reduction of the ketone.

Question 3

Why do you think the molecules are UV-active? [2m]

Answer: The acetophenone starting material and the reduced alcohol both contain phenyl/ benzene/ aromatic groups, which will absorb UV light.

Question 4

In thin-layer chromatography, the retention factor (Rf) is used to compare molecules. The Rf value of a molecule is equal to the distance traveled by the molecule divided by the distance traveled by the solvent front (both measured from the origin). 

a. What is the Rf of the starting material? [2m] Please show how you obtained your answer. 
b. What is the Rf of the product? [2m] Please show how you obtained your answer. 

Answer: 
a: (2.5-1.8)/2.5 = 0.28 
b: (2.5-2.2)/2.5 = 0.12 

Question 5

a. Based on their structures, do you think the starting material or the product is more polar? Why? [3m]
b. Do the TLC results agree with the polarity of the molecules? Why? [2m]

Answer: 

a. Product is more polar. It has an alcohol group which form hydrogen bonds, but not the starting ketone.
b. Yes, the product has a lower Rf than the starting material as the alcohol group enables it to interact more strongly/ hydrogen bond with the stationary phase.