Chemistry: Post your doubts here!

[Youssef Tawil]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
Number 39

 

[_Ahmad]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
Number 39

1) formula of butanone=C4H8O (mr of butanone =72)
yield=(44.64/72)*100=62%

2) formula of butanoic acid=C4H8O2 (mr of butanoic acid=88)
yield=(54.56/88)*100=62%

3) formula of 2 methylpropanoic acid =C4H8O2 (mr of 2 methylpropanoic acid=88)
yield =(54.56/88)*100=62%

for all options yield of product =62%
therefore answer is A

 

[Princess Raven]

Any one know why the answer is B? I keep getting the ratio for the second part to be 1:1 not 1:2

 

[Youssef Tawil]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
Number 7 and 8???? very hard . Anyone please explain them?

 

[GCE As and a level]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
Number 7 and 8???? very hard . Anyone please explain them?

Chemistry P1 all hard :s

 

[_Ahmad]

Any one know why the answer is B? I keep getting the ratio for the second part to be 1:1 not 1:2

 

[Youssef Tawil]

Chemistry P1 all hard :s

Hahaha i know but can u do these 2 questions? if u can please explain them. Thanks

 

[ZaqZainab]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
Number 7 and 8???? very hard . Anyone please explain them?

Q7 use
P1V1 = P2V2
5 x 12 + 6 x 10 = (10 + 5) x p
p =8
this is physics
Q8
use DATA BOOKLET for first and second ionization energy of Calcium 590 + 1150

 

[zainzul]

Did any one get the guess of Chem(As) practical 34 ?

 

[GCE As and a level]

Hahaha i know but can u do these 2 questions? if u can please explain them. Thanks

SRRY MAN
i cant :s

 

[forever_chocoholic]

Thanks buddy
same to you
well honestly speaking its not that bad compared to how hard the Paper 1 is
i usually get around 30 now a days i used to get 20 before it all becaus eof practice
but then coming to the gt they are too damn high for paper 1
you should score more than 30 to be on the safe side for paper 1
and as for paper 3 try just losing a mark or 2 or none cause paper 3 are very easy and they will safe you
InshAllah we all will get Good grades
as we want

InshAllah!

 

[forever_chocoholic]

can anyone explain
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w09_qp_12.pdf
Q:40

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_12.pdf
Q:24

pleaseee!!!

 

[Metanoia]

In Q.2 i don't understand how only 5 double bonds are broken?

Because the difference between the original structure and final structure is 10H. So we conclude 10H was added (5 C=C bonds affected).

 

[Metanoia]

how come an ionic bond formed?

Both 1 and 2 are correct

Ionic bond between ions of NH4+ and SO42-

 

[Metanoia]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_11.pdf Q19 ansC , Q22 ansA , Q27 ansD , Q36 ansA please help

s12qp11

Q19.



If wondering why not ans A, in the examiners approach, they don't view CO--> CO2 as spontaneous.

Q22. Products formed CH3CH2OH, CH3CH2COONa
% of CH3CH2OH = Mr of CH3CH2OH/(Mr of CH3CH2O- + Mr of CH3CH2COONa) x 100% = 46/(46+96) x 100% = 32.3%

Q27. C-I bond is weakest, so I- will be released quickest to form ppt with Ag+

Q36.

A. Higher pressure means more expensive equipment
B. Eqm shift to right as there are less molecules on right
C. Rate of backward reaction (and also forward reaction) increases because the gases become more concentrated at higher pressure

 

[Metanoia]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s07_qp_1.pdf
Q11
Q13 can someone explain?
Q16 why not D? thats how HCl or HI is formed by breaking I-I bond and Cl-Cl bond
Q18
Q21
Q39 which two alkenes i have problems with ring structures
Q40

S07qp1

Hi, please try to type the answers next to the questions so we can reply much faster.

Q11. The 2nd experiment has more moles of products but slower initial speed.
This can happen when we add a diluted solution to the original concentration
1) the number of moles of H2O2 increases --> more O2
2) the concentration of H2O2 decreases (due to dilution) --> slower production of O2

Q13. Focusing on Al atom, the Al is joined to N and 3 H, so 4 single bonds and no lone pairs around Al.

Q16. Question is trying to justify why it is forming of HI is harder (more endothermic).
Although statement D is true, just statement D alone actually meant that forming of HI is easier!

Q18. Fertiliser is NH4NO3

Q21. Need to replace a H of an alkyl group with halogen, need free radical substitution reaction.

Q39. When the OH is removed, a H from a neighboring carbon is also removed.
So the double bond could be between
1) the carbon( originally with the OH) and the carbon at the 6 o'clock position
2) the carbon( originally with the OH) and the carbon at the 1 o'clock position

Q40. Question says the reagent should be able to react with ester group. Of all 3 options, the acid is the one who can hydrolyse ester groups.

 

[Browny]

s04p1

Regarding Q28.

Key phrase in the question is "excess NaOH was used"
NaOH + SO3 --> NaHSO3 ---(1)
As there is excess NaOH, the HSO3- (acid) will further react.
NaHSO3+ NaOH --> Na2SO4 + H2O --(2)

Combine eqn (1) and (2), you will have the overall equation.
2NaOH + SO3 -->Na2SO4 + H2O

Q28. Tertiary alcohols can be oxidized by strong oxidizing agents (which is out of the syllabus), reason why they question use the phrase "not oxidized by mild oxidizing agents" is simply to reassure students that we are definitely talking about tertiary alcohols.

Q35 is as explained by ZaqZainab

Q19. Question is referring to NO2, are you asking about NO or NO2?

NO2, sorry.

 

[Browny]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_1.pdf

Can anybody please explain question 5 ans B, 9 ans B, 12 ans B, 18 ans C, 20 ans A, 38 ans A, please?

Some other problems are in question 11 why can't B be correct, 30 how to draw A and in 31 if a reaction is like from A to B and the energy change is +20 then if the reaction is from B to A is the change -20?

 

[Princess Raven]

Thank you

 

[Princess Raven]

Can anyone PLEASE explain these question!



Q5,7,17,18,24,25,30,33,34 from
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w05_qp_1.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w05_ms_1.pdf

I could answer 5,6,25,30,33 if u figure out the rest plz tell me how to solve them as well!