Chemistry: Post your doubts here!

[smzimran]

did u practice a lot in skl? and what was ur grade in it?

No, did around 8-9 in total throughout the year! LOL

 

[mehdi1028]

Can someone provde me wth the organc chemstry notes?? AS Level?

 

[DPratik]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_11.pdf

Q-14,22,25,30, 35 can someone please explain

for question 14) the answer is sodium cholride because there is one thing which you must look for to distinguish,chloride ion reacts with an excess of dil NH3,bromine ion reatcs with conc NH3 and Iodine ion doesn't react,so as the question has said the compound X reacts with dil NH3 which means the answer is sodium chloride !!!
for question 22) you can see check one by one,both the alcohols react the same way with KMnO4,both the alcohols react the same with Phosphorous Penatcholride and both react the same way with sodium but in the case of sulphuric acid,the longer alcohol chain may get oxidized where as the shorter chain won't get oxidized !!
for question 30) draw the displayed formulae and see that you can find both chiral center and cis-trans isomerism in D,you may find chiral center in B also but there is not cis-trans isomerism!!
for question 35) its obvious that in car engine carbon won't be form so that it will react in that way instead CO would be formed so the answer is nitrogen and sulphur !!

 

[DPratik]

The ans in C.How come the denominator is (0.07*0.02) ? Please explain..
View attachment 7373

as 1 mole of iodine and 1 mole of hydrogen forms two mole of mole of hydrogen Iodide.So at equilbrium when 0.26 mole of hydrogen iodide is formed which means 0.13 mole of iodine and 0.13 mole of hydrogen was used up so at equilbrium you got (0.15-0.13) mole of hydrogen and (0.15-0.13) mole of iodine left !!

 

[DragonCub]

If you read the question carefully enough, it states there's a cyclohexene ring and not a cyclohexane ring that the compound contains.
I guess there's no easier way to do this than to draw a quick small structure structure and count the number of hydrogen we're getting. :|

Alright... Then there are 13 C and 18 H left. (26-18)/2 = 4, so 4 double bonds in the aliphatic chain. Plus the one in cyclohexene there are 5.

 

[DPratik]

​

Can someone please give explanations to these paper 1 questions?​

​

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w08_qp_1.pdf​

Q3 What does 'ground state' mean? And r we supposed to write the '1s2 2s2....' electronic configuration to know the answer?​

Q21 Does an alcohol get oxidised by hot, concentrated manganate(7) ions?​

Q31 Why is the answer B not A? all the three statements seem correct.​

and Q38 Why cant the answer be B?​

ground state means when the electron are at the lowest level,yeah you are supposed to right it so that it may be easy for you to answer it

hey it surely would get becuase KMnO4 is an oxidizing agent which means alcohol can get oxidized

for question 31) you can see that there is the presence of most electronegative element of periodic table, N and O so which means permanent dipole can't form because both the element would try to attract the bonded electron towards itself !!


and for question 38) in fire extinguisher Br* free radical is generated to stop the combustion which means the answer must be option 1 and option 2 but i am not sure about why the answer is only option 1 but do note that in fire extinguisher Br * radical is generated !!

 

[selena]

please can anyone give me notes on isomerism and polymerization?

 

[hassam]

reply urgent for 2nd prt.....i guess there is insufficient info .......cos how will i know the mass of co2 lost

 

[tom ed]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w02_qp_1.pdf

can any body help me wd Q10 and 11......

 

[hassam]

well this is a definition of lattice energy the energy change when 1 mole of (ionic)
solid/crystals is formed from its gaseous ions.
er mentions candidates lost mark for not specifying that a solid was formed......is it necessaryy......cant l.e be used for ionic liquids

 

[DPratik]

hey can anyone provide me the notes of transition metals ? and worksheet of enthalpy changes(As) ??

 

[shan5674]

can someone explain or give me notes on chemical bonding and structure as well as enthaply cycles and calculations please

 

[JD REBORN]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
In Q34 why is statement 1 true?

 

[gary221]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
In Q34 why is statement 1 true?

i think its true bcoz since sulfuric acid is a stronger acid, it'll react faster, nn so reach a higher temp faster...

 

[JD REBORN]

i think its true bcoz since sulfuric acid is a stronger acid, it'll react faster, nn so reach a higher temp faster...

Sorry need a better explanation...

 

[JD REBORN]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s09_qp_1.pdf
Q11 Why cant answer be D
Q13 What to do in this?
Q31 How can radius be same?
Q34,Q35,Q37

 

[Jaf]

can any body help me wd Q10 and 11......

I can not believe it... question 11 took me half a page to do. -_____-

 

[gary221]

I can not believe it... question 11 took me half a page to do. -_____-

?

 

[Jaf]

?

There's way too much Algebra involved in the question. Any one not good at Mathematics will almost certainly screw this up.

 

[gary221]

ur damn right...
that is a teaser...
i think ill probably end up blind guessing ths ques...the time wont suffice