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Chemistry MCQ thread...

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Anonymousx3 said:
abdullah181994 said:
please please please answer this and explian your working

Is it C?
If my answer's correct, I'll explain it.

Isn't it C4H8?? What's the answer!

Mobeen said:
@saturation . ill look for 5 in the past papers and let u know ..

yeah, thanks alot, btw for the 4th qs, what are the 3 alkenes!?
 
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@saturation
ur q1 is june 2010 qp11 q22 and answer from mark scheme is B
 
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@Saturation
ur q2 is june 2010 qp11 q24 and answer in marks scheme is C
ur q3 is june 2010 qp11 q28 and answer " " " is D
ur q4 is june 2010 qp11 q29 and answer " " " is B
 
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abdullah181994 said:
@ anonymosx i also answered it c but the correct answer is D.

k.
I'm not completely sure, but maybe this is why:

You get 0.8 mol of both carbon dioxide and water. So the equation will look something like this:

0.2CXHY + 02 ----> 0.8CO2 + 0.8H20

So, to get 0.8 carbons, X needs to be 4 (0.2 X 4). And to get 1.6 hydrogens Y needs to be 8 (0.2 X 6).

Which means the answer is D - C4H8.

I hope that makes sense. If not, let me know and I'll try explaining again. :)
 
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abdullah181994 said:
@ anonymosx i also answered it c but the correct answer is D.

It's C4H8, :

0.2 mol produced 35.2g of CO2 and 14.4g of H20, which is 0.8 mol of CO2 and 0.8mol of H20

so now you have the ratio, 0.2 gave us 0.8, so 1 mol should give us 4 mol each. Now we have the balanced equation, so just adjust the number of carbon and hydrogen, to match equation:

CxHy + 6O2 = 4CO2 + 4H20

therefore, x = 4 and y = 8, so it's C4H8!
 
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Saturation said:
abdullah181994 said:
@ anonymosx i also answered it c but the correct answer is D.

It's C4H8, :

0.2 mol produced 35.2g of CO2 and 14.4g of H20, which is 0.8 mol of CO2 and 0.8mol of H20

so now you have the ratio, 0.2 gave us 0.8, so 1 mol should give us 4 mol each. Now we have the balanced equation, so just adjust the number of carbon and hydrogen, to match equation:

CxHy + 6O2 = 4CO2 + 4H20

therefore, x = 4 and y = 8, so it's C4H8!

Yeah, I got it. ;p
Thanks.
 
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@saturation my answers were correct and now u can even check them from mark scheme :p
 
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Mobeen said:
@saturation my answers were correct and now u can even check them from mark scheme :p

I know, but what about qs 5!? and what are the 3 alkenes for qs 4 pls! Thanks!
 
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Saturation said:
Mobeen said:
*for q4 is B ^
Thanks, but can you tell me what the 3 alkenes are!?
i dont know it either .. only know it because ive seen this question in past papers 2 or 3 times.. atleast now ur sure abt the answer because the marking scheme says so
 
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Saturation said:
Mobeen said:
@saturation my answers were correct and now u can even check them from mark scheme :p

I know, but what about qs 5!? and what are the 3 alkenes for qs 4 pls! Thanks!
ill search for q5 too ..
 
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abdullah181994 said:
thanks@ saturation

welcome! :)

Mobeen said:
Saturation said:
Mobeen said:
*for q4 is B ^
Thanks, but can you tell me what the 3 alkenes are!?
i dont know it either .. only know it because ive seen this question in past papers 2 or 3 times.. atleast now ur sure abt the answer because the marking scheme says so

haha , ok then, and yeah the qs do repeat! btw please let me know if you find qs 5! Thanks!
 
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saturation u were right .. q5 is D .. it is w08 qp1 q 38 . answer is D ..
 
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Mobeen said:
saturation u were right .. q5 is D .. it is w08 qp1 q 38 . answer is D ..

phew! so what I said earlier makes sense then? It's chloro flouro carbons which are used in extinguishers? (and btw some of the HALOGENOALKANES are extremely flammable!)

abdullah181994 said:
Some one please explian why graphite is more stable then diamond.

There was an entire disscussion about this earlier in this thread or in the another one. Here's what I remember: diamond to graphite is an exothermic reation, which means the products have less energy, so therefore they are more stable!
 
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