O Level Chemistry & IP Chemistry Notes by 10 Year Series Author - Chemistry Specialist

O Level Chemistry Made Easy

O Level Chemistry – Mini Series on Tough MCQs Part 4

Most of you would have finished most of O Levels Papers by now, and left with Paper 1 of Chemistry, Biology, Physics and Combine Science (Chem/Bio) or (Chem/Phy).

I realised that many students have started to have their holiday mood, and in fact already enjoying as though holiday has arrived.

Wait. Don’t get me wrong! Of course, it is important to relax awhile before their last papers, especially when their “last papers” are 1 week after the “second-last papers”. I can’t agree more that students should celebrate the little success, and enjoy abit of what they like to do during this one week, before their last papers. Students – You Have Been Working Hard! Kudos!

However, i must re-iterate that Paper 1 Examinations hold alot of marks for your subject. For example, Chemistry Paper 1 has a weightage of 40 marks which is translated to be 30% of your final Chemistry Grade. That is ALOT of marks to Score! So while you are enjoying now, do spend a few days to re-cap and practice more MCQs questions before your Chemistry Paper 1 next week.

Here is a couple of tricky MCQ questions that i have came across:

(Click image to have clearer view)

Question 1:
proton-number-1

PS:Remember to try out the questions and leave your answers and reasoning in the section “Leave A Reply” below

Question 2:
stability-of-metal-carbonates

Question 3:
reducing-agents-in-blast-furnace

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Sean Chua
Many know me as the Ten Year Series book author for JC A-Level H2 Chemistry and O-Level Pure Chemistry. My 19+ years of coaching experience (since 1999) with more than 1500 students from 180+ JCs and Secondary Schools has allowed me to understand the true reasons why students are not able to perform well in Chemistry. Most importantly, my strength lies in using everyday analogies (even grandmothers can understand!) to simplify abstract concepts. Also, my teaching methodology has been designed to be fun, enjoyable and effective for my students. If you want to have an enjoyable time learning Chemistry and being motivated to excel in Chemistry, contact me today at 98287357

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  3. For the portion of:
    ‘Carbon on the other hand reacts with Oxygen to form Carbon Dioxide so Oxygen changed from an oxidation state of 0 to 2- so it is reduced and Carbon should be a reducing agent’,
    rather than seeing it as oxygen losing 2 electrons, it can be seen as carbon gaining 2 oxygen atoms and therefore being oxidised.

  4. carbon monoxide is the reducing agent because it reduces Fe2O3 to molten iron (Fe) and takes up oxygen itself and becomes carbon dioxide. This is why it is the reducing agent.

  5. I agree with the other people on the first two questions. But I’m sorry but why is the answer for the last question B? Carbon Dioxide reacts with Carbon at high temperatures to form Carbon Monoxide in the chemical reaction CO2(g)+C(s)=2CO(g) so Carbon dioxide causes the Carbon atom to change from an oxidation state of 0 to 2+ so it has been oxidised and Carbon Dioxide should be an oxidising agent. Carbon on the other hand reacts with Oxygen to form Carbon Dioxide so Oxygen changed from an oxidation state of 0 to 2- so it is reduced and Carbon should be a reducing agent. The answer should be C. Will someone please clarify?

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