Chemistry Paper 2

[Maleeha]

Another question.. i dnt exactly remember the year but it was something like in a mixture of gaseous methane, ethane, propane and butane, whose droplets would be formed the first if the mixture is uniformly cooled down??? and please anyone who cud answer this.. do give me an explanation as well... thnx in advance =P

 

[ibadsiddiqi]

droplets of butane will be formed first. It is a general properties of alkanes that the physical properties gradually increase. The boiling points increases as the number of carbon atoms increases. As methane has the lowest number of atoms, it has the lowest boiling point. As butane has the highest number of carbon atoms, it has the highest boiling point. Therefore if the mixture is cooled, butane condenses faster then the others and hence, droplets of butane are formed first.
Hope you understood..

 

[no.mercy]

dont you think methane should form first as it has the lower boiling point :S

 

[Maleeha]

someone tel me please cuz i thinkk i wrote butane in my mock n got it wrong and my tchr encircled methane... but as i cant find my paper im not sure which one did i select n which one did my tchr encircle..

 

[no.mercy]

its methane..i think butane is wrong

 

[ibadsiddiqi]

methane can not form first as it has a very low boiling point. For example (just an eg) if the boiling point of methane is -100*C and that of Butane is -10*C. If the current temperature is 25*C and it is cooled to -20*C, droplets of butane will form as the temperature is now below the boiling point of butane while methane will remain a gas as the temp is still above its boiling point and methane is still a gas!
Hope this clears things

 

[Diamona151294]

these should be pretty simple but God knows why im getting confused......

The question was: draw structure of poly(propene)

In the marking scheme this was given:
– CH(CH3) – CH2 – CH(CH3) – CH2 – or full structural formula [1]
ALLOW: – [CH(CH3) – CH2]n –

The answer i wrote was -(c3h6)-(c3h6)-

What is wrong? and what does the ms thing mean??

Also isn't s present as S2?
In combustion eq they wrote S+O2=SO2
I wrote: S2+202=2SO2

 

[no.mercy]

@ibadsiddiqi dude if the temperature is 25 degree Celsius then methane is already in liquid form..lol..you are contradicting your own statement

 

[ibadsiddiqi]

No look..

 

[adnanj]

if the mixture is cooled, it means butane will be the first to be changed to droplets..I agree with Ibad..

 

[ibadsiddiqi]

No look..if methane boils at MINUS 100*C and butane at MINUS 10*C. The temperature is at 25*C, which means that both the substances are gases. Then if the temperature is cooled to MINUS 25*C then butane is a liquid while methane is still a gas as it boils at MINUS 100*C!
did you get it now?

 

[Maleeha]

cud anyone tel why is its answer stated B
Q15 http://www.xtremepapers.me/CIE/Cambridg ... _qp_11.pdf

 

[ibadsiddiqi]

B is correct as the rate of reaction decreases as the experiment proceeds because the acid is already dilute and as the experiment proceeds, it is losing its concentration. So as the conc decreases speed decreases

 

[Maleeha]

why isn't the answer C? :Search:

 

[ibadsiddiqi]

Because the rate of reaction decreases. In C, the rate is increasing at a decreasing rate while in B the rate is decreasing to zero. Did you get it now??

 

[Maleeha]

yea i thnk i sort of get it... thnx

 

[ibadsiddiqi]

yea sure. Now you should stop studying! seriously its 12! get some rest in order to be fresh for tomorrow!!

 

[Maleeha]

i jxt cant sleep wen i noe there's still so much to prepare =(

 

[Diamona151294]

In this i have problems in:

q1:why is it d?
Q4:i dont get the whole thing but the answer is c
Q10:i dont understand the question at all. the concept goes over my head. the answer is c
q29:why d?
Q32: the whole thing.Answer is d

Please please reply fast! and i posted one q on pg 5... pls answer dat too!!!
thanku in advance!

 

[workaholic]

yea sure. Now you should stop studying! seriously its 12! get some rest in order to be fresh for tomorrow!!

I cant sleep either... Will stay up uptil 2 knowing that I have to cover up for my bad ATP paper