How's it everybody?
I have only one mistake, the thing about kerosene uses. I don't memorise things, that's why :/
Alright, all the best for Bio everyone!
it is so hard!!!!!
then again i suck at chem
lol i doubt one can study chem without memorising. the paper is ok, got the colour of copper carbonate wrong. i didnt know it was green :x
i minus 3. One is careless about the humber of H in ester. Fark man. I forgot to count the H at the end of the acid.
another is kerosene
another one is the which combination wld not be suitable to produce co2. I didnt notcie insoluble.
not to mention the least % change in vol. Do you know about that?
actually, why is it that lead(ii) carbonate and sulphuric acid is not suitable for producing large quantity of acid? So what if the salt is insoluble?
I chose sodium carbonate + hydrochloric acid cos i tot it is hard to break the bonds since sodium is reactive
nah even if you memorise, you wont know kerosene is used for cooking. I rmb petroleum gas is used for cooking. so i was thinking if kerosene is needed in power station. but still chose A :(
Originally posted by davidche:i minus 3. One is careless about the humber of H in ester. Fark man. I forgot to count the H at the end of the acid.
another is kerosene
another one is the which combination wld not be suitable to produce co2. I didnt notcie insoluble.
not to mention the least % change in vol. Do you know about that?
kerosene: 2 uses airplane fuel and cooking/heating. i know this cos i read road dahl's matilda when i was a child! lollllll
lead compounds will produce little co2 when reacted with sulphuric acid, because lead sulphate is insoluble, forming a layer around lead compound, preventing sulphuric acid from reacting with the lead compound. thus little co2 produced in the case of lead carbonate
vol change is C, count the mols of gas, ignore liquid and solid
issit? i tot liquid occupies less vol. anyways i chose C. Dam insoluble layer. fark.
electrolysis question is A right, where cation of the electrolytes are different.
yeah. the qn about the total vol is still.......
Total volume question is pretty obvious. Solids and Liquids have negligible volume (24 dm^3 compared to 100 cm^3 or smth), so heck care them.
Electrolysis question is just out to confuse you. It is obviously A.
lead compounds will produce little co2 when reacted with sulphuric acid, because lead sulphate is insoluble, forming a layer around lead compound, preventing sulphuric acid from reacting with the lead compound. thus little co2 produced in the case of lead carbonate
Bingo.
Kerosene common sense what, people use to create arson one. So it's obvious for domestic cooking. But then I forgot aircraft also got the "VROOM" image behind its' engines.
No one can study chem without memorising? NO ONE? OMG.
can post your answers to compare?
From Q1 to Q40, man I need to sleep then study for bio later :P
DAACB DBADB CAAAC CDDAB ABDCD ACBBD
CBBAD BDABB
Bolded one is wrong one, not sure if got anymore mistakes though.
haha you have the same plan as me. ill compare now.
for qn 5, is it not insoluble in water? not all 4 atoms are connected to C if i am not wrong.
Hey, question 5 is C.
Silicon carbide is a poor conductor of electricity and is insoluble in water.
This is why I say Great Minds Think Alike :)
I'm not sure on that too, many of my friends put as insoluble in water, but since Carbon still has free hands, isn't it something like Graphite?
http://en.wikipedia.org/wiki/Silicon_carbide
Hell, I think all the answers were correct except D, just need to infer from diagram...
Silicon carbide exists in at least 70 crystalline forms. Alpha silicon carbide (α-SiC) is the most commonly encountered polymorph; it is formed at temperatures greater than 2000 °C and has a hexagonal crystal structure (similar to Wurtzite). The beta modification (β-SiC), with a zinc blende crystal structure (similar to diamond), is formed at temperatures below 2000 °C and is shown in the structure at the top of the page. Until recently, the beta form has had relatively few commercial uses, although there is now increasing interest in its use as a support for heterogeneous catalysts, owing to its higher surface area compared to the alpha form.
Silicon carbide has a density of 3.2 g/cm³, and its high sublimation temperature (approximately 2700 °C) makes it useful for bearings and furnace parts. Silicon carbide does not melt at any known pressure. It is also highly inert chemically. There is currently much interest in its use as a semiconductor material in electronics, where its high thermal conductivity, high electric field breakdown strength and high maximum current density make it more promising than silicon for high-powered devices.[3] In addition, it has strong coupling to microwave radiation, which together with its high sublimation point, permits practical use in heating and casting metals. SiC also has a very low coefficient of thermal expansion (4.0 × 10-6/K) and experiences no phase transitions that would cause discontinuities in thermal expansion.
Pure SiC is colorless. The brown to black color of industrial product results from iron impurities. The rainbow-like lustre of the crystals is caused by a passivation layer of silicon dioxide that forms on the surface.
o well heck care lar. tmr got bio. going to sleep now.
I need the natural allurance to sleep. I can't force-sleep. Kinda like insomnia.
if garrick was correct
i got 10 questions
wrong
one question is careless mistake
Qn 11 also wrong, the water is a liquid, not a gas.
So you cannot compare the ratio of water. Answer should be A
Originally posted by [e].Le-V:Qn 11 also wrong, the water is a liquid, not a gas.
So you cannot compare the ratio of water. Answer should be A
Maybe you would like to look more properly?
You are the one that should look more properly. Lmao
hmm but according to your theory. B can also be the choice right? Cos A and B are too alike. SO i chose C
Originally posted by davidche:hmm but according to your theory. B can also be the choice right? Cos A and B are too alike. SO i chose C
A and B alike? Erm...
A : 6 moles to 3 moles = decrease 50%
B : 7 moles to 2 moles = decrease ~ 71%
C : 3 moles to 1 mole = decrease ~ 67%
A and B don't seem to alike, and answer is clearly A... smallest % change.
say 2 mol of liquid occupies one mole of gas, its almost the same. Moreover you cant be sure it is 2:1. I think need to ask the pros here bout the qn lar.