Friday, September 28, 2007

helloo!!! okay, the answers for the chemistry practice paper:

Section B

B1(a)(i) Reagent: Aqueous Barium nitrate/lead(II)nitrate/calcium nitrate followed by dilute nitric acid.
Observation: White ppt formed insoluble in dilute nitric acid.

(ii) Reagent: Aqueous sodium hydroxide.
Observation: Green precipitate insoluble in excess aqueous NaOH.

(b) Anhydrous Iron(II)sulphate. Hydrated green crystals of iron(II)sulphate lost their water of crystallization and become white.

(c) X: Copper
Y: Sodium chloride
Z: Silver Chloride

(d) Magnesium is more reactive than copper and hence displace the copper ions from its solution to form copper metal which is reddish brown.

(e) Ag+(aq) + Cl-(aq) à AgCl(s)

B2(a) (i) Isotopes. and are both atoms of chlorine. They both have the same no. of protons which is 17 but different no. of neutrons. has 18 neutrons whereas has 20 neutrons thus different mass.

(ii) -. atom gains an electron to form - ion when reacting with metal.

(iii) Relative atomic mass of chlorine = (75/100)(35) + (25/100)(37)
= 35.5

(iv) this is supposed to be dot and cross diagram of Cl2O (chloride oxide)

(b)(i)
Name -Type of Structure -Electrical Conductivity(Molten State)
Silicon dioxide-Macromolecular -Does not conduct electricity
Calcium oxide -Ionic crystal lattice-Conduct electricity

(ii) SiO2 has macromolecular structure. Each Si atom joined to four other oxygen atom by strong covalent bond in a giant tetrahedral structure, all valence electrons used in bonding. Therefore, no free moving electrons to carry the electrical charges in any state. Ions in CaO held together by strong electrostatic forces of attraction in fixed position. In molten state, the ions are free to move hence able to conduct the electrical charges.

(iv) Calcium oxide is formed between Ca2+ and O2- ions whereas sodium chloride formed between Na+ and Cl- ions. The electrostatic forces of attraction between ions are stronger in CaO than NaCl because Ca2+ ion and O2-ion has a higher charge compared to sodium ion and chloride ion.

B3(a)(i) White solid: Magnesium oxide
Yellow solid: Sulphur

(ii) 2Mg + SO2 à 2MgO + S

(iii) MgO(s) + 2HCl(aq) à MgCl2(aq) + H2O(l)

(iv) SO2 2MgO 2MgCl2
No. of moles of SO2 = (4.0/32+2(16)) = 32.125 mol
No. of moles of MgCl2 = 0.120 mol
Max mass of MgCl2 formed = 0.120(24+2(35.5)) = 11.4g

(b)(i) No. of moles of CO2 = 18/24 = 0.75mol

(ii) CaCO3 CO2
Mass of CaCO3 = 0.750(40+12+3(16)) = 75g

(iii) % by mass of CaCO3 in sample = (75/100)(100) = 75%

Section C
C1(a) K+ and PO43-
(b)(i) Potassium hydroxide
(ii) H3PO4 + 3KOH à K3PO4 + 3H2O
(c) Titration mtd [1]
Correct steps [2]
Indicator usage + correct indicator [1]

(d)(i) Carbon dioxide

(ii)
Test: Bubble gas evolved into limewater
Observations: Limewater turned chalky/white ppt formed

(iii) Sodium is a reactive metal, it will react explosively with phosphoric acid which is dangerous.

C2(a) Beaker B

(b) Mg + Cu(NO3)2 à Mg(NO3)2 + Cu
Reddish brown/Pink solid deposited in the beaker. Blue solution slowly
turned colorless/fades to a lighter blue.

(c)(i) Beaker A and D

(ii) Aluminium forms a layer of protective oxide which is non porous and stick closely to surface of metal thus preventing aluminium from reacting with the solution.

(d) Calcium ion reacted with water to produce hydrogen gas.

C3(a) Correct steps and equations [3]

(b) Fe3O4

(c) Iron is a finite resource and hence need to be conserve.

(d)(i) Tin is unreactive and is used to prevent the food in the container from reacting with the steel alloy.

(ii) SnCl4

(iii) Small molecular structure. Weak Van Der Waals forces of attraction between tin(II)chloride molecules. Little energy needed to overcome these forces. Therefore m/pt low.

sorry if its too messy... im bullshit with computers... heh, u guys will have to make do with this nonsense... so sorry hor.

`qin-

L ones are crappy~
10:26 PM

Close up view of Jiu Kong (Samuel)

L ones are crappy~
8:03 PM

Friday, September 21, 2007

The ultimate art of Shao Hua is finally done:
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By the way it is Anselm here. Shao Hua cannot post the pic himself as his internet encountered some problems. He wants to mention that the pic he edited contains NO PERSONAL ATTACKS, although he uses Jia Qi's head 3 times! LOL

Enjoy!

L ones are crappy~
5:24 PM

Thursday, September 13, 2007

just to let u all preview wad i'm doing now....
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So sweet. haha. take that wayne.
More to come in future.

-SH

Meanwhile let's look at the original, and wait patiently for the shao hua version!

Anselm

L ones are crappy~
5:39 PM

Wednesday, September 12, 2007

hahaZ! the exact same thing i blog in my blog. -.-

blogging about something special: coppyriiiteee 3L1 -Bored Game!

description:

it's specially for bored L1-ians during free periods, if you dun want to do homework. it's nice to play, and it really kills of boredom as it has alot alot alot of RETURN TO START. confirm will keep your laughing your heads off!

we have a normal version, caterpillar & ladder version and monopoly version(photo not included).

founder- Ahmad
Developer- Janice, WeiQin, Cordelia

Members- Leon, Aloy, Boon.

interested parties please apply @ this pink table:

-well, mayb not exactly... but nearly there-

janiicee'
http://jzanc-r.blogspot.com

L ones are crappy~
4:11 PM

Wednesday, September 5, 2007

For those who haven't got enough of the teachers' day pictures. ahhahaha.

That's about it.

:D see you guys soon.

Wahidah

L ones are crappy~
8:14 PM

Saturday, September 1, 2007

teachers' day ::3L1 '07::

okeh L1s.. lets admit it. friday was a blast! in fact, for me its the best tchers day ever in my bpghs life.. =) SOO.. lets give a very special thanks to all those who have put in soo much effort in making it a success..

first of all.. lets thank JIA QI, SHAO HUA, ALOYSIUS and JUN TAO for helping out in the arranging of tables. (thought they might feel offended) LOL.

secondly, the mini celebration in class. =D
1) JIA QI. he organised it. & he was the emcee! ppl, recall his speech and laugh.
2) ANSELM. do i need to tell you what he did!? he put in much effort in practising and memorising the moves. APPLAUD!
3) ALL OF YOU L1s. im sure mrs wong appreciates your msg. WAHIDAH, DIYANA, HAZWANI, HERIANTI, GEELYN, AHMAD & I nice-ified them.. btw ppl, the gift was wahidah's idea and she'd like to say thank you for the msgs!
4) ..those of you who brought cameras. Nadia 3P1, thanx for taking the photos for us! =)

& of course, those who worked their arses off cooking food for the huge appetite of 3L1..
1) WAHIDAH. thanks for letting us mess your house cooking til 12.30am! ppl, the tasty pizza and donut biscuits are HER recipes.
2) HAZWANI. that cheesecake is awesome.
3) WEIQIN. i think ya'll still rmb that crunchy nachos with superb salsa sauce!
4) JAU & IQBAL. the delicious sausages which disappeared very quickly.
5) HIDAYAH. love that fried rice!!
6) DIYANA. without her, there'll be no drinks & you'll probably be eating rice off your palm.
7) JANICE. her mudpie was too nice! ..until DICT ate it with fried rice.
8) AMIRAH. well that yummy instant noodles was pretty easy to cook. =)

oh & SHAO HUA. nice video!
..for those i didnt mention, thank you too!

so yea, mrs wong really loved everything and was really happy. SO THANK YOU 3L1!!!

<3
AMIRAH

L ones are crappy~
12:19 PM

Whew. I spent 4 hours doing this and finally finished. haha. in case u all didnt know wad he was dancing to i've added music and subtitles.
Enjoy :)
-Shao Hua

L ones are crappy~
11:02 AM

Friday, September 28, 2007

Friday, September 21, 2007

Thursday, September 13, 2007

Wednesday, September 12, 2007

Wednesday, September 5, 2007

Saturday, September 1, 2007

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