HKDSE Chemistry Question Review (2025-07-26)

Question 1: Below is the structure of Vitamin B8:

(a) Give the trivial name of this compound.

(b) Is it a carbohydrate? Explain briefly.

(c) Is it a non-polar compound? Justify your answer.

Solution:

(a) Inositol

(b) Its molecular formula is C6H12O6, so the answer is in the affirmative.

(c) It is NOT a planar structure, so stereoisomerism exists, so it is a polar compound.

Question 2: Below is the structure of paracetamol:

(a) Give the trivial name of this compound.

(b) Explain why it is said to be derived from petroleum.

Solution:

(a) Panadol

(b) 3 main structures are observed:

1. phenol

2. amine

3. carbocylic acid

Except 2, all can be derived from petroleum:

1. adding a hydroxy group from benzene

3. complete oxidation of ethane

Question 3:

Calcium acetate is soluble in water.

(a) Write its chemical formula.

(b) Account for its solubility.

Solution:

(a) (CH3COO)2Ca

(b) Acetic acid is a weak acid, so when ionized in water, the escaped proton is less likely to be recombined, making thr acetate ion stable, so its metal salt are all soluble.

making the acetate ion stable

Question 4:

Which of the following food contains more amino acids?

Boiled eggs, Scrambled eggs

Solution:

Scramble eggs have less peptide bonds such that it looks more liquid. Hence, they have less amino acids to be condensated.

Hence, they have more remnant amino acids to be condensated.

Question 5:

Explain why testosterone is a carcinogen.

Solution:

It accelerates lipid consumption in both men and women, but excess concentration will lead to free radicals escaping from the catabolism of fats, then men runs more risk of developing prostate cancer, as the gland will secrete fructose which will be converted to fatty acids when in excess.