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GCE ‘O’ Level 2010 Oct/Nov Chemistry 5072 (MCQ) Paper 1 Suggested Answers & Solutions

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Tuition given in the topic of Little Miss Loi the Science Tutor (archived) from the desk of at 2:27 am (Singapore time)

Hello again and unfortunately, the weekend of tuition classes has definitely caused me to keep you non-partying folks waiting for the Pure Chemistry MCQ solutions, and me staying up late to finish them:

2010 O-Level October/November Chemistry 5072 Paper 1 Suggested Solutions

A much more sedate Pure Chemistry Paper 1 compared to the relative mayhem over at the Physics side, though it does have its usual tricks up its sleeve.

In any case, do leave the usual mistake/typo-spotting comment and I’ll try to attend to you once I find the time (admittedly we’re a little behind the comments due to the weekend of classes 🙁 )

Okie good night for now!

Revision Exercise

To show that you have understood what Miss Loi just taught you from the centre, you must:

1. Doe commented in tuition class

2010
Nov
14
Sun
3:12am

1

Excuse me, do you know how much must i get for paper 2 in order to get a a1/a2 if i scored 30/40 for paper 1? Thanks a lot!

2. hmmm... commented in tuition class

2010
Nov
14
Sun
7:59am

2

hey ms loi i'm just a passer by here..
anyway, why cant question 2 answer be B?
isnt copper(II) carbonate green? hence, the answer blue ppt formed should be wrong?
and lastly, could you explain question 12?
why is it B but not C?

thank you

• Ray replied to hmmm...’s comment

2010
Nov
14
Sun
12:01pm

2.1

@hmmm...: @hmmm... the answer to question 12 is definitely B. The enthalpy change of the forward reaction is between the energy of the reactants to the energy of the products. The question is asking from the peak of the activation energy of the forward reaction to the energy of the products, thus this is the Activation energy plus the enthalpy change of the forward reaction. This it is the Activation energy of the reverse reaction, since haber process is a reversible reaction.

• J replied to hmmm...’s comment

2010
Nov
14
Sun
12:52pm

2.2

@hmmm...: the colour of CuCO3 varies from blue to green, so the choice wasn't wrong. In choice D, NaOH and NaCl will be produced whereby both are soluble compounds. However on the table, it showed that a white ppt will be produced.

Therefore if youwere to compare in the strictest sense, D is definitely incorrect while B is correct if you give the choice the benefit of doubt that the CuCO3 produced is blue.

Trick question i would say cause many of my friends jumped into conclusion that B was the answer without observing the remaining choices.

3. Anon commented in tuition class

2010
Nov
14
Sun
10:46am

3

Do you know roughly what's the percentage to get A1 for this year's paper? Will the bell curve shift by a lot?

4. kino commented in tuition class

2010
Nov
14
Sun
12:30pm

4

Hello,
I have some questions about Q29,
Why cannot the answer be D?
Haematite should contain impurity such as sulfur as it was mined.
The oxygen will oxide the sulfur in the haematite and form sulfur dioxide.
However, I am not very sure whether sulfur dioxide is considered as the "main gases" or not...
The another reason I think B is not the answer is nitrogen in air should form oxide of nitrogen due to the high temperature. Thus, the answer should not involve nitrogen gas.
Thank you m(_ _)m

• tormented replied to kino’s comment

2010
Nov
14
Sun
3:01pm

4.1

@kino: Hi kino. For the sulfur dioxide thingy, as what you've said, its not a main gas, partly bcoz haematite contains mainly iron(lll) oxide. And for nitrogen dioxide, as nitrogen(triple bond) is more inert than carbon, more of the oxygen will react with the carbon to form carbon dioxide or monoxide. And also since there are about 70% of nitrogen in air, not all the nitrogen will react with oxygen, even though under high pressure and temp, to give a substantial amount of nitrogen dioxide. So even have nitrogen dioxide form, it will be so little that its not considered 'main gases'. If you are using the Marshall Cavendish Chem Matters txbk by 4 authors, Pg 245 at the bottom last 2 lines lie the answer. Hope this helps. Actually I also wrote D, but nvm.

5. Kelly commented in tuition class

2010
Nov
14
Sun
12:37pm

5

My teacher said A1 is roughly 83%

For question 2, it should D because there is no way a ppt. would form as all Group 1 metal in compounds will be soluble in water.

On the other hand, for option B, copper(ii) carbonate can range from blue to green in colour (but more green). But if you look at the question carefully, they said aqueous sodium carbonate, which means the ions present include H+,Cu2+,OH-,CO32-. When added to Copper(II) sulfate, a little blue ppt will appear partly because of the precipitation of copper(ii) ions from cuso4 as the hydroxide ions from sodium carbonate, forming blue precipitate of Copper(II) hydroxide.

Though the colour is predominantly green, the slight blue ppt that forms should be able to make it less obvious that its enitrely and distinctly green.

6. butter commented in tuition class

2010
Nov
14
Sun
2:29pm

6

can i ask if anyone knows where i can find h2 chem p3 answers? 🙁

7. cass commented in tuition class

2010
Nov
14
Sun
2:39pm

7

hie, err..for qn 28, i thought the answer should be C since the silver metal deposited on the copper wire will like prevent further reaction so the mass of the silver crystals should not increase gradually? and is it above mean if i get 36/40 if i count my qn28 wrong? thanks

8. Gladys commented in tuition class

2010
Nov
14
Sun
3:23pm

8

Thx 4 ur explaination J. U must have done well in order to explain to us... I did badly only scoring 21/40... ): how bout the rest of u here?

9. val commented in tuition class

2010
Nov
14
Sun
4:51pm

9

what's the mean score for last year in order to get a1 or a2?

10. Jax commented in tuition class

2010
Nov
14
Sun
7:03pm

10

Haiz i got 23/40. What are the chances of a B?

11. cheese commented in tuition class

2010
Nov
14
Sun
7:48pm

11

not a bad paper.. i got 38/40. could have gotten full marks T_T!!! hope i can score a A1 hahaha.

12. Heath commented in tuition class

2010
Nov
14
Sun
8:13pm

12

Hi miss Loi, do I still stand a chance to get an A1 if I scored 38/40 and 37/40 for chem and physics paper 1 respectively? :/

13. Sugarrrrush* commented in tuition class

2010
Nov
15
Mon
4:33pm

13

Will getting 30-32/40 (give and take that there's a few answers I corrected at the last minute) guarantee me an A? (I don't need an A1, just an A2 will do), considering that I did pretty well for P2 but screwed up the last chem SPA?

14. Fred commented in tuition class

2010
Nov
15
Mon
7:06pm

14

Ms loi, can you post the pure bio paper 1 mcq? Thanks in advance 🙂

15. Anon commented in tuition class

2010
Nov
15
Mon
10:58pm
16. pearl777000 commented in tuition class

2010
Nov
15
Mon
11:26pm

16

hi miss loi,I'm just passing by n I have doubts abt qn31.shouldn't the answer be helium n not flourine because helium has 8outermost electrons while flourine only has 7?thanks:)

17. junkbox commented in tuition class

2010
Nov
16
Tue
12:27am

17

18. junkbox commented in tuition class

2010
Nov
16
Tue
12:28am

18

19. Krystal commented in tuition class

2010
Nov
18
Thu
9:52am

19

Hi, i'm Krystal. i can't open the files for the gce o level answers. they say we have to change the encoding to make the file readable but none is suitable. do you know what i should do to make the files readable? or could you convert the files and sent them to my e-mail address?

20. hi commented in tuition class

2010
Nov
22
Mon
6:06pm

20

1. 2010
Nov
14
Sun
5:20am
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