Chemistry: Post your doubts here!

[hihi]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_12.pdf

Q 7 , 8, 12, 14, 22,
28 why isnt it A or C ?

Explain please !

for 28: u do not write H in skeletal formula
for 14 try working out with M(Ca(NO3)2 )

 

[nazzzzzz]

What's that reaction involved with KMnO4 and alchohols? I can't seem to understand. Please help me I need an answer desperately

 

[angelicsuccubus]

because Mr of H2=(2*1)=2
moles=mass/mr
moles=120/2
moles=60
same for moles at equilibrium

aack thanks.. sorry I haven't done chem in so long.. I was taking the 3 in 3H2 in account too

 

[Casablanca]

What's that reaction involved with KMnO4 and alchohols? I can't seem to understand. Please help me I need an answer desperately

Oxidation.

 

[Goku]

Ermm anybody got tips for MCQ exams?
All the choices look so alike,and the calculations are </3 :'(

 

[Muhammad Asif]

What's that reaction involved with KMnO4 and alchohols? I can't seem to understand. Please help me I need an answer desperately

its the oxidaton reaction a primary alcohol(if completelyoxidised under Hot concentrated condition) is oxidised 2 a carboxyhlic acid .....if incomplte oxidise(cold dilute) then can form aldehyde.......secondory alcohols are just oxidised 2 ketones in both conditions.....

 

[angelicsuccubus]

What's that reaction involved with KMnO4 and alchohols? I can't seem to understand. Please help me I need an answer desperately

KMnO4 or KCr2O7?

 

[Goku]

What's that reaction involved with KMnO4 and alchohols? I can't seem to understand. Please help me I need an answer desperately

KMnO4 oxidises alcohols to aldehydes or ketones, and then rapidly oxidises the aldehyde to a carboxylic acid if you let it react.

 

[Student12]

for 28: u do not write H in skeletal formula
for 14 try working out with M(Ca(NO3)2 )

Very helpful !

 

[angelicsuccubus]

its the oxidaton reaction a primary alcohol(if completelyoxidised under Hot concentrated condition) is oxidised 2 a carboxyhlic acid .....if incomplte oxidise(cold dilute) then can form aldehyde.......secondory alcohols are just oxidised 2 ketones in both conditions.....

but isnt that with K2Cr2O7, acidified with dil H2SO4?

 

[Muhammad Asif]

but isnt that with K2Cr2O7, acidified with dil H2SO4?

the concern is not with which acid you acidify it......the thing is both KMNO4 and K2Cr2O7 are acidifed.....thats it

 

[misha321]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q11

 

[Casablanca]

How many isomers with the structure C5H10 have structures involving pi bonds?

A. 3
B. 4
C. 5
D. 6

Why?

 

[Oliveme]

Thank you, donor.

 

[LimeReem]

I'm soo doomed.. I don't know how to answer most of the questions... I don't know what to do. :

 

[Student12]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_12.pdf

Q 7 , 8, 12, 14, 22,
28 why isnt it A or C ?

Explain please !

SOMEONE !

 

[KurayamiKimmi]

God bless,thankyou!
You made it seem so easy..

glad i could be of help ^_^

 

[Casablanca]

Ermm anybody got tips for MCQ exams?
All the choices look so alike,and the calculations are </3 :'(

-Start backwards. It saves time.
-Use process of elimination. You may not know what is correct, but you might know what is wrong, so don't worry about those options and focus on the others. (Especially useful in the last 10 questions)
-Use trial and error. Where possible, plug in the values from answers, and work the equation backwards to figure out which one is correct.

 

[Student12]

I'm soo doomed.. I don't know how to answer most of the questions... I don't know what to do. :

Its alright, all you can do now is try understanding what people are posting and the answers or go through some of the notes. Don't get tensed AT ALL ! it wont help in any way.. relax whatever you know just do it tmrw and whatever you can do nw just do it may it be little. Something is better than nothing. There are many in the same situation. Just an advice

 

[angelicsuccubus]

the concern is not with which acid you acidify it......the thing is both KMNO4 and K2Cr2O7 are acidifed.....thats it

so either one, gives the same result, yeah?