Finally … after working out a total of 180 MCQs in the past days, I’m at the end of my 2009 ‘O’ Level Science MCQ nightmare crusade!
2009 O-Level Oct/Nov Chemistry 5072 (left) & Biology 5094 (right) MCQ Paper 1 Suggested Solutions – click to download
As usual hope the explanations will help clear up some doubts on these rather tricky papers this year. And, for the last time, please leave a comment if you spot any mistake, typo and/or disagree with any of the explanations given.
Now that the massive stimulation of A1 receptors and grade regulators in my hands and hypothalamus respectively is over, it’s time for my neurons to join those of all O-Level 2009 students and assume their refractory period … YAY!!!
*drops dead*
39 Comments
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Goodness gracious..! I got 34/40 for Chemistry and 36/40 for Biology..! I think I did relatively ok but I kinda disagree with some of the answers..!
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Miss Loi, for Biology p1 Q 36, I think the answer should be D..! Two heterozygous mice will result in 3 brown: 1 white. Since, the first three mice are all brown, so the next mouse would definitely be white..! So the chance that she would be correct must be 100% what?
And Q38, I thought C should be adaptation and not evolution? Why is the answer not D?
And finally Q39, shouldn't the answer be B? Isn't the crop plant growing faster and producing a higher yield an ECONOMIC advantage?
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question 34 answer should be D I think for chemistry and question 33 for chemistry is also rather ambiguous since option D also seems to be correct
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For Chemistry Q34, why is it not D? The hydrocarbons get smaller when further up the column, so shouldn't the Mr of the hydrocarbon at the top be the smallest?
Q11, why is it not B,iodine?
Lastly Q13, I don't understand it at all..!
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@GX: For question 11, number of atoms is calculated by the number of moles X the Avogadro constant, which is estimated to be 6 × 10^23. Thus for the four options, find the one with the biggest number of moles, which in this case, is carbon.
And for 13, copper sulfate is dissolved in water.The 5 moles of H2O doesn't matter, since it is in water, thus the only ions are Cu ^2+ and SO4 ^2- .
Hope this helps! :3
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Chem question 34 should be D.
A is wrong- For example the topmost fraction is petroleum gas,a mixture of methane, ethane...
Bio question 38-
I think C is not evolution. A new species of tigers have not resulted and i think it should be adaptation instead.
Nature selects the best suited elephants for surviving by depriving the weaker elephants of food. Hence natural selection has occured.
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yup.. for chemistry, question 34 sounds wrong.. I do think tt a better answer should be D since a mixture will be collected at every column and thus A should be incorrect.
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For me, i think question 34 is D too. Also, why is question 23 D? hydrogen chloride does not have any acidic property unless it dissolve in water to form H+ ions.
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I believe that bio Q38 should be D, as the problem is not mainly about the lack of food, but the competition for this scared resource of food.
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Hi ,i am very grateful to you for posting your ans . All seemed right and logical for me except for Qn 38.
Shouldn't it be D?
Cause evolution is a collective process that takes place in a long time span of millions of years.
Natural selection is a better answer cause "only the fittest survive"
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Hey, just wondering, why isn't the answer for chem qn 1 "melting" instead since the whole process is taking place at a constant temperature?
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Can you predict the marks for an A1 and A2 grade for all sciences? Thanks 😀
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yea for chem 7n 34 the textbook chemistry matters under pg 381 it says "Each petroleum fraction is a mixture opf hydrocarbons which boil over a certain temperature range' so answer shld not be A
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Hi Miss Loi,thanks so much for posting your answers!
However for question 11 in the chemistry MCQ,shouldn't it be (D) oxygen instead of (A) carbon reason being,they asked for the largest amount of ATOMS and oxygen is diatomic.So you have to take the no.of moles for oxygen,times 2.Oxygen will then contain the largest amount of atoms?
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@ yellowred. to find the no. of atoms, you gotta multiply the no. of moles with Avogadro's Constant. So carbon got the largest no. of mole. hence its the answer
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@gx read my comment to yellowred on q11.
q13: Copper2 sulpate will dissociate in water into cu2+ and so42- ions. however, i quite disagree with all the answers there, because the solution will also contain h+ and oh- ions. i hope Miss Loi can further discuss this question.
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@flap
well not quite true. Because when u boil off the sugar solution u get the sugar back. so it doesnt melt. they just diffuse into the water molecules
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@ flap but if u wish to argue that the constant temperature is at the temperature which the crystals will melt, the bad news is that your water will be totally boiled off first before your sugar turns black.
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Sorry guys for being away after I've posted this yesterday.
On hindsight, looking at the comments, maybe I should have split this into two blog posts 😛
But anyway, first and foremost yes the answer to Chemistry Q34 is indeed D.
As described in your textbook, fractions of crude oil are made up of hydrocarbons (e.g. alkanes, alkenes etc.) in varying quantities, so those that reach the top of the column would be the smaller molecules (i.e. molecules containing lesser number of carbons) which possess lesser amount of intermolecular forces, and therefore lower boiling points.
Option A is incorrect because we have multiple compounds existing within each fraction collected (e.g. petrol consists of alkanes/alkenes etc.)
I've quickly amended the answer to Chemistry Q34 and updated its explanation. Sorry for missing this out.
Now for the rest of the queries ...
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got 37/40 for bio (if qn 38 ans is D) and 39/40 for chem...
evolution's definition includes the change of ancestral forms to new forms... so C cant be the ans...
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OK for the rest of the Chemistry queries:
Q1: Flap, firstly, melting occurs at a constant temperature but it also has to occur at a specific temperature. As the question didn't indicate the value of the constant temperature, we cannot assume that it is the melting point of the sugar.
Secondly, melting occurs when the sugar crystals get heated up in the absence of water. In the question our sugar crystals are instead placed in a beaker of water. Since sugar crystals are soluble in water, they will dissolve in water and the sugar molecules would spread evenly throughout (diffusion) the beaker of water.
Besides, as andrew has kindly pointed out, the boiling point of water is lower than the melting point of sugar 😉
Q11: yellowred, to find the number of atoms in a 1g sample:
No. of mole of atoms in sample x Avogadro's constant
= (mass of sample)/(Ar or Mr of sample) × no of atoms in a molecule × Avogadro's constant
Carbon and Iron exist as C and Fe respectively, so we use their respective atomic masses (Ar)
⇒ no. of mole of 1g of C or Fe atoms
= 1/(Ar of C or Fe) × 1 atom × 6 × 1023
Iodine and Oxygen exist as I2 and O2 respectively, so we need to consider their respective molecular masses (Mr)
⇒ no. of mole of 1g of iodine atoms or oxygen atoms
= [1/(Mr of I2 or O2)] × 2 atoms × 6 × 1023
= [1/(2 × Ar of I2 or O2)] × 2 atoms × 6 × 1023
Notice how the 2s cancel themselves out in the calculation for iodine and oxygen?
Q13: Andrew, the absence of an option for 4 moles is due to water being a covalent compound which doesn't readily or completely dissociate into H+ and OH− ions.
A slight positive charge is found on H and a slight negative charge on OH within one H2O molecule due to the electronegativity nature (i.e. the ability to attract electrons towards itself in a covalent bond) of oxygen, resulting in 'pseudo' H+ and OH− ions (though admittedly the attraction of oxygen on the shared electrons is so strong that the H2O molecule can sometimes break up into H+ and OH− ions - but the probability of this happening is almost negligible)
Whereas, CuSO4 is an ionic compound. It dissociates into Cu2+ and SO42− ions readily and completely when dissolved in water.
Therefore, strictly speaking, the solution contains only two types of ions i.e. Cu2+ and SO42−. And thus every one mole of CuSO4 would give one mole of Cu2+ as well as SO42−.
Q23: ab, actually hydrogen chloride readily becomes aqueous hydrochloric acid when it comes into contact with atmospheric traces of water vapour.
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And now for GX's Biology queries ...
Q36: Errr ... childbirths are independent events (i.e. present childbirth is not affected by previous childbirths). In mice, we have a 75% chance of getting a brown fur baby and a 25% chance of getting a white fur baby every time a female mouse gives birth, according to the F1 phenotypic ratio.
Furthermore, the female mouse is not restricted to giving birth to just 4 babies, in which 3 must be brown and 1 must be white.
Case in point, though there's a 50% chance of getting a boy and 50% chance of getting a girl in human pregnancies, not all of us end up with two children, in which 1 must be boy and the other must be girl.
Q39: Herbicide is often used to kill unwanted weeds which threaten the growth of the crop plant (and reduce its yield) by competing with them for the available nutrients. But at the same time, herbicide is harmful to the crop plant.
By modifying the crop plant to be resistant to herbicide, we could safely use the herbicide to kill weeds with no worries that the growth (and economic yield) of the crop plant would be threatened.
Option B is not the best option since it suggests that being resistant to herbicide will allow the crop plant to grow faster though there is no direct relation between the two. Other factors e.g. quality of soil affecting their growth should be taken into consideration instead.
Hence, the best answer should be the one describing an economic advantage arising from a direct consequence of the modification made.
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Hey, Miss Loi, thanks for clarifying my doubts! My oh my, I would say that the MCQs are tricky and really require much thinking in depth..!
So after the amendment, I got 35/40 for Chemistry and still 36/40 for Biology. Oh and for Physics, I got 33/40.
My teachers told me that a score of about 35 is expected for students taking pure sciences. Don't you think the expectations are a bit too high..? I mean really, it doesn't always guarantee a distinction...!
Lastly, as mav mentioned, what do you think the chances of distiction for the sciences would be like?
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And now for the big debate on Biology Q38, here's my reason (in addition to what I've written in the solution) for my choice of Option C. But feel free to discuss further and hopefully we can all come to a common consensus on the final answer:
Selection must result in reproductive success, allowing favourable alleles to be passed on to successive generations. Survival alone does not guarantee reproductive success.
In option D, if natural selection has occurred, it should imply that the next generation of young elephants (the keyword here is young) produced by the stronger elephants would not die due to lack of food, as the favourable alleles have been passed on to them.
Evolution occurs due to a combination of two factors, selection and chance (genetic drift). The selection process is adaptive, and responds by favouring genotypes adapted to the new conditions.
In option C, nature will over the years keep selecting those mountain tigers with alleles that give rise to thick fur phenotype, so that they could successfully adapt to the cold environment, survive, reproduce, and pass on their genes to the next generations, resulting in the evolution (a new species) of mountain tigers with a thicker layer of fur.
Note that new alleles are not produced on demand, so this implies that the mountain tigers do not produce new alleles to develop a thicker layer of fur.
Instead, evolution must have occurred through combination of several cycles of adaptive selection and/or chance effects to give rise to the population of mountain tigers with a thicker layer of fur.
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how about question 23? why is the answer D? hydrogen chloride does not have any acidic property. it only acts as acid when dissolve in water to form H+ ions.
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ab: Errr ... *points to the end of Comment #20
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Would there be moderations for comb sci(phy+chem)??
If so,what would be the estimated mark to get an A1??
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Before i start.. il just tell frankly tat ive lost the bio paper1. Urm if u dnt mind... u do remember abt the question which asks which if these requires multiple receptors across the body before it carries out its processes. Urm, pls tell the qn no. , answer and explain it if possible so tat i can check wit my fren. Many thanks. O yea.. pls give a rough gauge of wat an A1 is for bio . Thanks!
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Hi Apple,
I can only reply you now as I didn't have the question papers with me when I was overseas the past week.
I've since scanned through the Biology 5094 and the Combined Physics/Biology 5117 papers and the only question I could find that says something about "receptors" is Q25 (about effectors & receptors in the eye) in the pure bio paper, but this doesn't seem to relate to what you're asking.
Can you provide me with more info that you can still recall?
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Hello Ms Loi.
With regard to the biology paper 1, question 36, shouldn't the answer be (50%).
That's due to the fact that every birth is independent of each other and that the ratio that has been derived is based purely on mathematical probability.
Thus the chances of the girl getting it right would be a clear 50%, either a straight yes or a no.
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Hi teacher,
I am having problems with the Biology 5090 Paper 1 2008 OCT/Nov Paper Q12.I cant seem to differenciate which os the xylem and the phloem.
Thanks Guru...
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Hi Andy,
Actually, if you see the diagram below, it's not purely by mathematical probability that the chance of a boy or a girl being born is 50%! 😉
Let X and Y be the sex chromosome, Y being the male-determining chromosome in most mammals:
Vigneiswaran: Hmmm ... seems like your Q12 is different from mine. Are you from Singapore? The subject codes for Singapore's 2008 O-Level Biology papers are 5094 and 5100 (there's no 5090).
Do you have the question with you?
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Urrmm...I am from Malaysia....Not taking the singapore syllabus....Urmm yea I do have the question with me....Shall post it to you??
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Vigneiswaran: Yes you may take a photo of the question and send it to my sister's email and I'll take a look at it.
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Teacher..cant I create another discussion board for my type of syallbus....the 5090....cause there are questions I wana ask you and I am quite afraid your students might get confused though..lol
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Vigneiswaran, you've got mail 🙂
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Got it..Replyd it :*)
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Hi , will 5116 phy/chem mcq answers be up anytime soon ?
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@Hello: *waves*