Chemistry: Post your doubts here!

[SilverCrest]

AOA EVERYBODY

This question does not make sense to me .The answer is C.I have eliminated options A and D by myself.What really confuses me is how polyethene melts over a range of temperature ,and paper does not.
Mixtures are supposed to melt over a range of temperature right?

6 A substance commonly found in the house or garden has the following properties.
• It is combustible.
• It is an electrical insulator.
• It melts over a range of temperature.
What could the substance be?
A brass
B paper
C poly(ethene)
D silicon(IV) oxide


Please can anyone explain the concept tested in this question?

Thanks!

 

[AbbbbY]

ahha... well do we have the option of ATP in cambridge chemistry?

Nope.

 

[Haider Nisar]

wanted to knw abt how many marks are needed to get an A in chemistry for a levels m/j 2013

 

[DumbIdiot]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_42.pdf

no. 3(c)

for MgBr2, how come that br2 is formed and not o2?

 

[AbbbbY]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_42.pdf

no. 3(c)

for MgBr2, how come that br2 is formed and not o2?

MgBr2

Mg = -2.38
Br2 = -1.07
O2 = -0.40
H = 0.00


AgF
Ag = 0.8
F = 2.87
O2 = -0.40
H = 0.00

FeSO4
Fe = -0.44
SO4 = 0.17
O2 = -0.40
H = 0.00


According to the values:

Anode:
MgBr2: Br2
AgF: O2
FeSO4: O2


Cathode

MgBr2: H2
AgF: Ag
FeSO4: H2

Get it?
You just need to see the values.
If you don't get the chapter, i.e how to choose values, I'll suggest you read up the chapter on chemguide. Very good stuff there and very well explained.

 

[DumbIdiot]

MgBr2

Mg = -2.38
Br2 = -1.07
O2 = -0.40
H = 0.00


AgF
Ag = 0.8
F = 2.87
O2 = -0.40
H = 0.00

FeSO4
Fe = -0.44
SO4 = 0.17
O2 = -0.40
H = 0.00


According to the values:

Anode:
MgBr2: Br2
AgF: O2
FeSO4: O2


Cathode

MgBr2: H2
AgF: Ag
FeSO4: H2

Get it?
You just need to see the values.
If you don't get the chapter, i.e how to choose values, I'll suggest you read up the chapter on chemguide. Very good stuff there and very well explained.

the values are all positive
+1.07 for br2
+0.40 for o2
+2.87 for f2

then how come, under the same conditions br2 is released rather than o2.

the value of both halogen are more positive than that of 02.

there is another reaction involving the release of 02 whose value is +1.23 and is more than that of br2 but less than f2

h20 = o2 + 4h+ + 4e

is it because this reaction is occuring that br2 is being released rather than 02 or is the first reaction occuring and i am missing something?

 

[beeloooo]

can anyone solve this please and also let me know the reason for it ? please its urgent

 

[Ahmed Raja]

As level combustion moles, could any one help me out?

 

[AbbbbY]

As level combustion moles, could any one help me out?

What part of the combustion moles?

Could you post a few questions. Easier to explain that way.

 

[Rickster]

Hi there,
I need help with with questoin 3 a , 3b.
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_41.pdf
Also just wondering, which part of the syllabus is this question from?

Thanks

 

[Abhi Mevawala]

guyzzzz Q4 (f) iii
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w04_qp_2.pdf
how did the double bond between carbon atoms come after the reaction (check in MS)

 

[Kinki Tiffany 12]

Ca2+: 0.099nm
Zn2+: 0.074nm
Pb2+: 0.120nm

which one has the smallest radius? im confused

 

[AbbbbY]

Ca2+: 0.099nm
Zn2+: 0.074nm
Pb2+: 0.120nm

which one has the smallest radius? im confused

Zn 2+

Is 0.074 smaller or 0.099 smaller?
Still confused? is 74 smaller or 99? (eat up the mutual x.0's)

 

[Abhi Mevawala]

plzz guyzzz slove my doubt

 

[messi10]

guyzzzz Q4 (f) iii
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_2.pdf
how did the double bond between carbon atoms come after the reaction (check in MS)

I think remove the double bond and put a Br on one Carbon and H on other carbon.

Whenever an HBr reacts with alkene, one H is added and other Br.
If it would Bromine gas (Br2), then Br would be added on both carbons.

 

[Abhi Mevawala]

but check out the MS they havent removed the double bond

 

[deane26]

Where to start?? for A2. All my topics are mixed up... T.T

 

[Minato112]

can anyone solve this please and also let me know the reason for it ? please its urgent

Apart from B, all C-atoms are coplanar. For C-atoms to be coplanar, there must be less than or equal 3 C-atoms bonded to each other. As soon as there are 4, it changes shape and in most cases become tetrahedral. Hoe this helps.

 

[Minato112]

guyzzzz Q4 (f) iii
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_2.pdf
how did the double bond between carbon atoms come after the reaction (check in MS)

The organic question u mean?

 

[Abhi Mevawala]

ya

The organic question u mean?