Here are the suggested answers for O Level Chemistry Paper 1, worked out by our O-Level Chemistry Tutor Mr Eric Lee (Mr Lee is also our H2 Chemistry tutor). Detailed explanations will be posted soon. Answers for paper 2 will be posted soon too.
– Remember: you only have 1 hr to complete 40 questions, that is a maximum of 1 hr 30 sec for each question with zero time for checking at the end of the examination.
– My advice is to spend 1 minute for each question so that you can some extra time to come back and think about the questions you skipped and also do a quick check of your answers (e.g. whether you shade your answers correctly or not).
– Don’t spend too long on ONE question. If you don’t know, just skip first. Don’t waste time on ONE question you don’t know and rush through the last 10 questions towards the end when time is running out. The last 10 questions may be the easy questions to be answered!
– Shade your answers IMMEDIATELY. You can circle the answers on the question book but DO NOT leave it to the last minute to transfer your answers. If you have limited time towards the end, you will rush through the shading and most likely you will shade wrongly. You just need to miss one question for the whole shading process to turn into a disaster.
– Do your calculation questions fast and accurate, take note of careless mistakes.
– Remember the solubility rules at your fingertips and your Qualitative Analysis.
– Read the four options given to you. Do not rush into selecting the option you THINK is correct. Remember to always choose the BEST answer from the four options. Sometimes, 2 options may seem correct at first glance but you are to choose the BEST answer. You need to convince yourself that the other 3 options are WRONG. And you have to do this within the time limit.
– Be confident of your concepts. Study hard and you will excel in your Paper 1.
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CALL 65694897 OR SMS 98530744 OR 97860411.
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Hi, we tried to rush it out. This might not be the most appropriate suggested solutions. Feel free to comment and discuss. Let me know if I make mistakes. Thanks!
Also, we might not respond too fast as we will be trying to do the paper 2 for h2 math later too.
ERRATA:
4(ii) I made a silly mistake substituting the equations back in. You should get (4, 18) and (8,6) as the answers.
The following is a suggested solution by our H2 and H1 Math Tutor, Mr. Teng. Please note that it is a suggested solutions and was rushed out. Mr. Teng omitted several presentation steps out of convenience. There might be alternative solutions at times too. Feel free to comment and discuss. Please let us know if there are mistakes too. Thanks in advance.
PLEASE NOTE THAT STUDENTS ARE EXPECTED TO WRITE STATE YOUR DISTRIBUTIONS CLEARLY. We omitted for convenience.
Disclaimer: This suggested solutions is provided free by Mr. Teng & Singapore Learner. Both parties do not profit from this. We simply believe that this will help current students and future students to learn from the mistakes of others. Thanks.
ERRATA & Remarks:
6(ii) I miscounted and was careless.
Case 1: A plays midfield, B sits out of attacker =>3c1 x 8c4 x 4c1 x 5c4
Case 2: A sits out midfield, B plays attacker => 3c1 x 8c4 x 4c2 x 5c3
Case 1 + Case 2 =1 6800
(iii) I doubled counted indeed. Thanks for pointing out. Should be
Case 1: Midfielder A plays midfield => 8c4 x 3c1
Case 2: Midfielder A plays defender => 8c3 x 3c2
Case 3: Midfielder A sits out => 8c4 x 3c2
3c1 x 5c4 x (8c4 x 3c1 + 8c3 x 3c2 + 8c4 x 3c2) = 8820
8ai. I drew the left side of the quadratic. It should be the right side. my bad.
9. I initially used Z-Test for this question. But T-test is definitely more appropriate as we are given as unknown population variance. I changed it to T-test in the following solutions, but understand that some teachers consider Z-Test to be acceptable too. I should highlight that nobody has access to the actual answer scheme; we only see the marker’s report.
(ii), (iii) Set notations should be used. {t>3.48} and {0<k^2<0.423}
11. Please take note that I used CLT here, so cc is not required.
– I understand some students misunderstand that CLT is used to find the mean of any distribution. This is a terrible misconception. CLT is a limiting theorem, and we apply it to approximate a non-normal distribution to a normal distribution, given n is sufficient. And they can be sum of independent random variables, sample sum, or sample mean. You can read more from the link below.
– Why I used CLT approximation instead of poisson approximation (Poisson approximation is not incorrect either): I used continuity correction in qn 7 alr, so given examiner psychology, I would think they want to be impressed with something different. That’s why I picked CLT approximation. Do note that this does not mean that doing poisson approximation is wrong; so long as you perform cc precisely.
I do hope this clarifies, and I’m sorry it came late as I was ill and had jc1 classes yesterday too.
The following is a suggested solution by our H2 and H1 Math Tutor, Mr. Teng. Please note that it is a suggested solutions and was rushed out. Mr. Teng omitted several presentation steps out of convenience. There might be alternative solutions at times too. Feel free to comment and discuss. We will try our best to answer.
Errata:
Qn3 I misread it. Answer should be 2/3 and need not be evaluated.
Qn5i I copied wrongly off GC. answer should -3+4i. It shouldn’t affect the back parts.
Qn7 I copied wrongly off GC. So rounding off, the answers should α=1.885(3dp)
Those who thought new media and social media concerns make a ‘hot’ topic, got our way – sort of. It turned out to be the topic of the passage in Paper 2.
The inequality question emerged yet again – this time with a narrower focus on workers’ rights.
The current affairs question helped those who heeded the reminder to, well, BE CURRENT.
The other reminder was THINK BIGGER / DEEPER. Those who chose the broad question about always getting what we want may have included :
– self-actualisation and other innate desires
– the need to consider the impact on our values & our treatment of others (e.g. Are their rights sacrificed ? Do our relationships suffer ? What or How much are we prepared to lose ?)
– the struggle to balance aspiration and other conflicting responsibilities
– the consideration of whether what we want is really good for us, or just a perception
– the good and bad of material pursuits
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The Tutor for our Chemistry program isa former MOE school teacher (ex-Rafflesian) who has been coaching students in Chemistry, Physics and Mathematics for more than 10 years. An alumnus of RI and RJC, he also holds both a Master of Education degree and a Postgraduate Diploma in Education with Credit from the National Institute of Education (NIE), as well as a Bachelor of Science degree from the National University of Singapore (NUS).
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@ BLK 644, BUKIT BATOK CENTRAL, #01-68. S(650644).
1(i) When t = 0, 20 + A = 80, so A must be equal to 60.
1(ii) k = 0.288 (to 3 SF)
1(iii) Since t > 3.82, it is safe to give the food 4 min after removal from the microwave.
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2(i) Remainder = – 12
2(ii) f(-2) = 0, so (x+2) is a factor of f(x). Solving f(x) = 0, x = -2, 1/2 or 3.
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3(i) Length of rectangle = 9/2 + Sqrt(3)/6
3(ii) c = -1
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4(I) 2.25 4
(ii) 8x^2 + 5x + 64 = 0
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5(a) x^2 – 8x + 32 = 0. No real solution because discriminant is less than 0.
5(b) y = 1/x^2
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6(I) Use the fact that triangle ACE is isosceles and the alternate-segment theorem to state that angle ACE = angle ABC. Angle DEF = angle ECA + angle EAC.
6(ii) angle DFE = 2 x angle ACB.
6(iii) Use the fact that angle BAC = 180 deg – (angle BAF + angle CAE).
So 2 x (angle BAC) = 360 deg – 2(angle BAF + angle CAE).
6. (i) Remember that when there is a mixture of trigo functions which cannot fit into a single trigo identity, convert all the given trigo functions into sine and cosine. Start with the LHS, the more complicated expression. You will reach the key stage where
8. Integrate f'(x) to get f(x) with a +c. Use f(pi/2) = 0 to get c = 1/4. Differentiate f'(x) to get f”(x)= 4cos4x + 2sin2x. Proceed to add f”(x) to 4f(x) to get the RHS.
9(i) Pure inequality question. Solve 2x^2 + 5x – 12 > 0 by sketching a quadratic graph. Ans: {x : x < -4 U x > 3/2}
9(ii) Show that the (b^2 – 4ac) of (4x^2 + 4x + 1 = 0) is zero.
