Chemistry: Post your doubts here!

[xxfarhaxx]

Guys need help on these as quick as possible, exam's in four days!​

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w06_qp_1.pdf​

http://www.xtremepapers.com/papers/...and AS Level/Chemistry (9701)/9701_w06_er.pdf​

​

Q6 Why not B?​

Q11 used a long method to solve it but ended up guessing the answer. ​

Q23 Why not A or D?​

Q23. not A cz thr r 3 hydrogens bonded to da carbon group.
Not D coz 3 methyl groups r bonded

 

[Student12]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_1.pdf
Q2- The answer is B ? explain plz.

 

[xxfarhaxx]

View attachment 8291

If the first division was 0.5 then the second division should be 1.0 then A isnt correct. As 1.0 moles of oxygen doesnt correspond to Al

hlp me with ma othr questions plzzzz..c above

 

[xxfarhaxx]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_1.pdf
Q2- The answer is B ? explain plz.

wel i gues one is 35 n 37 n da othr one is myb 34( cz its cl+ ions)...nt vry sure

 

[Gémeaux]

Assalamoalaikum wr wb!

Got some doubts in P1
Got some doubts in P1

View attachment 8282View attachment 8283View attachment 8284View attachment 8285View attachment 8286View attachment 8287View attachment 8288View attachment 8289

26. A is dehydration, C is acid hydrolysis of esters. D is mixture of ketone and an oxidizing agent, and ketones do not oxidize. B is an aldehyde with an oxidizing agent which will oxidize aldehyde, and reduce itself... a redox reaction occurs.

40. such reaction pathway diagram will only be of a reaction that consists of two steps occuring separately for the reaction to cmplt. this happens when tertiary haloalkane will react with NaOH in an SN1 mechanism.

20. A fits into the description given. B does not react with aq. NaOH. C is a gas at 25°C. D does not mix with water cmpltly.

35. Solubility of group II metals increases down the group so Ba is more soluble than Ca. Ca will form a white suspension and Ba will dissolve. Both being alkaline earth metals will turn litnus blue. and in each case H2 will be produced.

37. contaminants mainly are two: N2 and S. the question says X is solid so sulphur will be the option. continue on now with S. its oxide SO2 is formed in car engines? yes. it *cud* be oxidized if provided with suitable conditions.
1)SO2 has lone pairs as it bonds with 2 atoms of Oxygen. 2) without vanadium pentaoxide (catalyst) the reaction cannot occur spontaneously in atmosphere. 3) SO2 is colorless.

hope it helps =)

 

[histephenson007]

There are two possible isotopes for Cl. But the molecule is Cl2. So, there can be three possible peaks.

1. 2 atoms of 35Cl form a Cl2
2. 2 atoms of 37Cl form a Cl2
3. 1 atom of 35Cl and 1 atom of 37Cl form the Cl2.

I dunno what the (+) charge on the Cl2 is about. But I think it has something to do with the mass of an electron being negligible.

 

[roadtrip9o9]

Solve these PLEASE http://www.xtremepapers.com/community/threads/chemistry-mcqs-help.14133/

 

[melly713]

I don't know about 29's reason but I know that Alkene obtained from dehydration of but-2-nol will have 3 isomers so 3 alkenes. So B

For 30, Please view the picture in full size otherwise you'll find it too small:

http://img685.imageshack.us/img685/8421/001jwvf.jpg

Remember there is no need for writing down full structures as you obviously won't have enough time but I did to explain it. Just have a look at only the double bonded carbons for cis-trans isomerism, if they have any 1 similar element or group on both side it shows cis-trans isomerism.

Similarly only look at single-bonded carbon for optical and see if any carbon has 4 different groups or elements surrounding it.]

] hey for the pic im seeing a photo of a frog in an icecube im not seeing anything else?

 

[melly713]

hi

i dint get 29.... but got 30
30 30 Which compound exhibits both cis-trans and optical isomerism?
A CH3CH=CHCH2CH3
B CH3CHBrCH=CH2
C CH3CBr=CBrCH3
D CH3CH2CHBrCH=CHBr

a compound which contains both optical isomer ( a C compound with 4 different group, a chiral centre) and a cis-trans isomerism

a- cannot be optical, as non of the carbon is a chiral centre,whereas it has cis-trans isomerism.
b-does not have cis-trans isomerism
c-has cis-trans but not optical isomerism
d -has both cis - trans and a chiral centre
you have to draw and workout , and you will get the right answer
so d is the answer.
hope you understand, if u dont pls ask the doubt

how can i look for a chiral if there is a double bond ? im only seeing 3 groups?

 

[melly713]

] hey for the pic im seeing a photo of a frog in an icecube im not seeing anything else?

bu i understand #29 thanx

 

[Most_UniQue]

Can someone explain me what are chiral compounds with examples? I searched the net but cudnt understand

 

[melly713]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s09_qp_31.pdf lab paper
plz help with #1 C (ii), (iii) and (iv) thanx.

and..
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s10_qp_31.pdf #1 H thanx

 

[XPFMember]

25: First one: cracking, requires high temperature
2nd and 3rd: Substitution reaction, require heat
So D remains

37: Y is CO dude

20: no other option is right

Aoa wr wb!
jazakAllah khairen..thnx a lot

...i actually didnt know substituition reactions require heat i probably forgot

 

[Most_UniQue]

Aoa wr wb!
for 20, why not ethanol? :s

and jazakAllah...i actually didnt know substituition reactions require heat i probably forgot

i didnt quite get 37

Substitution reaction requires heat? I didnt know that!

 

[XPFMember]

25: First one: cracking, requires high temperature
2nd and 3rd: Substitution reaction, require heat
So D remains

37: Y is CO dude

20: no other option is right

Substitution reaction requires heat? I didnt know that!

 

[Anoushay]

Hey,can anyone explain the question number 13 in this paper? thanks.
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf

 

[XPFMember]

..
hope it helps =)

Aoa wr wb!

JazakAllah khairen...It did help a lot..

thnx again ..

 

[namraahmad]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_43.pdf Que 10 a (iii) please someone explain???

 

[rehan751]

] hey for the pic im seeing a photo of a frog in an icecube im not seeing anything else?

Oh I don't know its opening fine here but I have attached it with this post also. Try now.

 

[melly713]

Oh I don't know its opening fine here but I have attached it with this post also. Try now.

View attachment 8295

oh ok i see now thanx !