Chemistry: Post your doubts here!

[..sacrifice4Revenge..]

Every one can do mistakes
Especially with this great SUBJECT

yeah right, 'Chemistry the Great'

 

[kingo44]

chemidtry iam aliveeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

 

[GCE As and a level]

chemidtry iam aliveeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

I think that we are only physically aliveeeeeeeeeeee

 

[..sacrifice4Revenge..]

chemidtry iam aliveeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

No shit sherlock!

 

[GCE As and a level]

..sacrifice4Revenge.. http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_12.pdf
Q20
Q25

 

[unique111]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s07_qp_1.pdf
Q12- How is B even possible?
40-How does carboxylic acid react with an ester

Q12) https://www.xtremepapers.com/community/threads/chemistry-mcq-thread.7567/page-2#post-98170
Q40) my mind is boggled! :s

 

[..sacrifice4Revenge..]

..sacrifice4Revenge.. http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_12.pdf
Q20

ok,
ive went over this question thrice, doing it the wrong way everytime but with the correct answer, idk how
now had to do it correctly,
ok so the products are
propanol, and sodium ethanoate
calculate their MR
60 and 82

now mass of propanol
60/82 X100
= 42.3%
so C

 

[MYLORD]

Friends i dont know what to do enthalpy questions
It sticks to my head like a leech

 

[..sacrifice4Revenge..]

..sacrifice4Revenge.. http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_12.pdf
Q20
Q25

25

it is an activated complex involving 5bonds of carbon.
so has to be C or D
now, in D. C has a negative electronegativity charge which is wrong
so is C,which is correct in all ways

 

[..sacrifice4Revenge..]

Friends i dont know what to do enthalpy questions
It sticks to my head like a leech

use this


If given only heat of combustions, then use heat of combustion of reactants - heat of formation of products

If given only heat of formation, then use heat of formation of products - heat of formation of reactants

If given only bond energy, BE of reactants - BE of products

 

[MYLORD]

use this


If given only heat of combustions, then use heat of combustion of reactants - heat of formation of products

If given only heat of formation, then use heat of formation of products - heat of formation of reactants

If given only bond energy, BE of reactants - BE of products

thnx bro

 

[unique111]

Q12) https://www.xtremepapers.com/community/threads/chemistry-mcq-thread.7567/page-2#post-98170
Q40) my mind is boggled! :s

Q 40) now that I think of it, the question is asking for ester hydrolysis. It is hydrolysed by water or by dilute acids. The only acid here is ethanoic acid, despite being a weak acid, it is still an acid. :/

 

[AhsanAfzal]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf
Q19 H3PO4 is weak acid, then why is the answer A?

 

[GCE As and a level]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_11.pdf
Q6
q11
Q17
q21
Q24
Q26
Q38

 

[saffe]

Two equilibria are shown below.

reaction I 2X2(g) + Y2(g) 2X2Y(g)
reaction II X2Y(g) X2(g) + )g( 2
1Y 2

The numerical value of Kc for reaction I is 2.

Under the same conditions, what is the numerical value of Kc for reaction II?
Answer is 1 over square root 2

 

[saffe]

the question is in the picture too

 

[MYLORD]

guys any last tips ?????!!!!

 

[GCE As and a level]

guys any last tips ?????!!!!

GO and SLEEP
Give ur self a break
BEST OF LUCK

 

[AhsanAfzal]

• guys any last tips ?????!!!!

  
  Lets pray for each other and ace the test with the help of Allah !!!
  

 

[..sacrifice4Revenge..]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_11.pdf
Q6
q11
Q17
q21
Q24
Q26
Q38

6- use PV=nRT to calculate number of moles
multiply the moles with Mr of Ammonia

q11- A, since if u divide the Enthalpy with N u will get of a single X-Y bond.
q17-calculate moles from PV=nRT
divide the mass by moles to get Mr and check against periodic table
21-D, since if you add C2H5, there will be two of them one one side, two C2H5 on the second Carbon and so no cis-trans.
24-c, cz u need to break the double bond and insert a OH on the second carbon which would be oxidised to ketone in the next step.
26-c, cz u need to remove a chlorine from one carbon and that same carbon has to be a radical
38-1 is correct, so is 2., basics. 3 is not because Alcohols dont undertake such substitution to form halogenoalkane