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Chemistry: Post your doubts here!

M

Muhammad Asif

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misha321 said:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q11
Click to expand...
the answer is C since the moles of CO2 produced=atoms of CO2:
1mol=24dm3thus 24000cm3
mols that occupy 72cm3=72/24000
moles that occupy72cm3=3*10^-3
so carbon atoms=3*10^-3
mass of this carbon atoms= 3*10^3*12(mr)
mass=.036g
mass of almunium=mass of compund-mass of carbon atoms
mass of almunium=.144-.036=.108
moles of Al=mass/Mr
moles=.108/27=4*10^-3
mole ratio of Al:C ------>4*106-3:3*10^-3
thus simple ratio is 4:3
so compound is Al4C3
 
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misha321

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Muhammad Asif said:
the answer is C since the moles of CO2 produced=atoms of CO2:
1mol=24dm3thus 24000cm3
mols that occupy 72cm3=72/24000
moles that occupy72cm3=3*10^-3
so carbon atoms=3*10^-3
mass of this carbon atoms= 3*10^3*12(mr)
mass=.036g
mass of almunium=mass of compund-mass of carbon atoms
mass of almunium=.144-.036=.108
moles of Al=mass/Mr
moles=.108/27=4*10^-3
mole ratio of Al:C ------>4*106-3:3*10^-3
thus simple ratio is 4:3
so compound is Al4C3
Click to expand...
thankyou
 
M

Muhammad Asif

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Oliveme said:
Please answer questions 22, 24, and 34. Thank you very much. :)

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w09_qp_12.pdf
Click to expand...
Q22=plymerise 1-2 dichloroethene and then hydrolise it all Cl will be replaced by OH giving the plymer shown......
Q24=the intermediate is a +charged carbocation which react with electrophile Br...thus accepts 2 electrons from it...so acceptor of pair of electrons is a electrophile.....
Q34=Sulphuric acid is not a product of a reaction of (NH4)2SO4+Ca(OH)2....thus answer is automatically C...still you need prove for Q34 i can do that
 
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nazzzzzz

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Goku said:
KMnO4 oxidises alcohols to aldehydes or ketones, and then rapidly oxidises the aldehyde to a carboxylic acid if you let it react.
Click to expand...

Thanks so does that mean when KMnO4 oxidises alchohol to carboxylic acids and ketones respectively it is turned from orange to green? Therefore it gets reduced?
 
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hm12

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Casablanca said:
No idea. I don't have the marking scheme. ._.
Click to expand...
i dont know if i am right because i suck at these drawing and counting the numbers thingy questions but here is what i came up with

1)CH2=CHCH2CH2CH3
2)CH3CH=CHCH2CH3
3)H-C-(H)=(H)-C-CH2CH2CH3 i am trying to draw a cis isomer here i hope you get the structure
4)H-C-(H)=(CH2CH2CH3)-C-H the trans isomer
5)CH3-C-(H)=(H)-C-(CH2CH3) cis isomer
6)CH3-C-(H)=(CH2CH3)-C-H trans isomer
 
Oliveme

Oliveme

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Muhammad Asif said:
Q22=plymerise 1-2 dichloroethene and then hydrolise it all Cl will be replaced by OH giving the plymer shown......
Q24=the intermediate is a +charged carbocation which react with electrophile Br...thus accepts 2 electrons from it...so acceptor of pair of electrons is a electrophile.....
Q34=Sulphuric acid is not a product of a reaction of (NH4)2SO4+Ca(OH)2....thus answer is automatically C...still you need prove for Q34 i can do that
Click to expand...
can you please elaborate? thank you.
and another question pls. explain in detail.
Question 7 http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf

Thank you so very much :)
 
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