2021 Victoria School Sec 4 Chemistry Prelim Paper 1 Analysis

In this chemistry tuition blog post, I’ll share more on the 2021 Victoria School S4 Chemistry Prelim Paper 1 analysis.

Victoria School 2021 P1 - VS Chem 2021 Sec 4 Prelim Paper 1

Victoria School 2021 P2 - VS Chem 2021 Sec 4 Prelim Paper 2

Victoria School 2021 P1 & 2 Ans Key - VS Chem 2021 Sec 4 Prelim Answer Key

Let's dive into 3 specific questions that cover the following topics in this Chemistry Prelim Paper Analysis - Chemical bonding, Acid & Bases & Periodic Table) for this paper analysis. (Question: #7, #15 & #24)

Question #7: Chemical Bonding 

To start answering this question, you should learn to identify the topic tested - Which in this case is Chemical Bonding.

The electronic configuration can seem confusing to some, but you can always add an element to it to see a better picture.

W is Carbon, X is Oxygen, Y is Fluorine & Z is Potassium.

1. WX₂ → CO₂ (Yes, there is such a compound & the boiling point is below room temperature!)
2. XY₂ → OF₂ (Yes, there is such a compound & the boiling point is below room temperature!)
3. Z₂X → K₂O (Yes, there is such a compound, BUT this is an ionic compound with a high boiling/melting point.)

Therefore, the answer is A.

Question #15: Qualitative Analysis

To start answering this question, you should learn to identify the topic tested - Which in this case is Qualitative Analysis

Next, we should start with the colourless gas that turns moist red litmus blue (NH₃) & with the presence of Aluminium metal (as a reducing agent), we can conclude that X contains NO₃⁻ ions.

And since we see a blue solution throughout the whole diagram. The ion is Cu²⁺. Therefore, we can conclude that W is Cu(NO₃)₂.

Cu(NO₃)₂ + NaOH → NaNO₃ + Cu(OH)₂  | Cu(OH)₂ + H₂SO₄ → CuSO₄ + H₂O 

X → NaNO₃

Y → Cu(OH)₂ 

Z → CuSO₄ 

Question #24: Periodic Table

To start answering this question, you should learn to identify the topic tested - Which in this case is the Periodic Table.

The colour intensity increases down group VII → since iodine is a black solid, Astatine will also be a dark colour solid.

Florine being at the top of Group VII, it is the strongest halogen (Oxidsing agent).

The oxidising power decreased down the group since it is further away from the positively charged nucleus, making it harder to gain electrons.

So, Astatine is weaker than Iodine.

Lastly, since At is a less reactive halogen than HBr → the compound formed by HAt will be weaker compared to HBr thus, LESS thermally stable. (A)