Chemistry: Post your doubts here!

[Hinafatima]

please,may i get helped in q# 29 and 35 for may june 2013 variant 13 , answers are D and C respectively?thanks

 

[Zepudee]

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

Propyl ethanoate
Propanol and sodium ethanoate
ch3ch2ch2oh and ch3coona
Mr= 60, Mr= 82
Total product Mr = 142
So, % propanol = 60/142 x 100 = 42.3%
%ch3coona = 82/142 x 100 = 57.7%
Hence, C

 

[kingo44]

Plz attach the link of the year and tell us the number of Q so that we can help u man

When santonin is first treated with warm dilute H2SO4, and then the product of this reaction is
treated with cold acidified KMnO4, a final product X is obtained.

How many atoms of hydrogen in each molecule of product X can be displaced with sodium
metal?
A 2 B 4 C 5 D 6

 

[loveyuan]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_qp_1.pdf

9\\21(no sunlight wheyyy)\\33\\37 pleaseeeee

 

[ashcull14]

..

 

[loveyuan]

When santonin is first treated with warm dilute H2SO4, and then the product of this reaction is
treated with cold acidified KMnO4, a final product X is obtained.

How many atoms of hydrogen in each molecule of product X can be displaced with sodium
metal?
A 2 B 4 C 5 D 6

D6
when h2so4 added the -Coo bond ester bond break down and acid and alcohol form
+ col KMnO4 the double bond all gone and form 4 -OH group
sodium can react with acid and alcohol .
each of the acid and alcohol replace by sodium
so 6 of the hydrogen atom

 

[kingo44]

woooooooo what

 

[kingo44]

so whenester bond is broken only one hydroxyl group and one cooh group is formed right then na substitutes them to get alkoxide right

 

[Metanoia]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_11.pdf
question 29
idono why i cant solve isomer question everytime !!!! TT

An easy, albeit time consuming way to figure these questions out is to simply draw the isomers. You know there's a double bond, so it must show geometric isomerism - cis and trans, that makes 2. But they aren't asking for just geometric isomers, they're asking for all the isomers. Another one would be but-1-ene. So that makes 3. I know this isn't the best way to work it out, but it's better than nothing.

The question says 'structural or otherwise' :S I don't know, I could be wrong.

Could you or someone else help me with the questions I posted earlier? Just on the previous page.

but there is a differenc betweeen structural and stereo isomers isnt it :/?

well i think the cis and tra wont be included in this one :/

For this question, all isomers, structural, geometric (cis-trans) and optical (chiral) have to be considered.

Besides the 2-methylpropene the other 3 isomers are as mentioned by MaboroshI_I



Its just that for C4H8, there is no chiral carbon, for we need no consider that part.[/quote]

 

[ashcull14]

donno wht mistake am i committing

 

[ashcull14]

help urGENT PLZZZZZZZZz

 

[kingo44]

View attachment 45074

who i n helll will think to do this correct only 1 mark omg jesus christ the merciful

 

[Metanoia]

MJ 2008 Q27!!!some1 plz explain

s08qp1

Q27.
Use the 4 options and trial and error.

Before dehydration, the C=C bonds were actually CH-COH.

Check which of the 4 could possibly give us a tertiary alcohol (resistant to oxidation) before dehydration.
View attachment 44341
In this case, it was D.

 

[Metanoia]

so whenester bond is broken only one hydroxyl group and one cooh group is formed right then na substitutes them to get alkoxide right

ester bond broken by acidic hydrolysis --> alcohol and COOH group
ester bond broken by alkaline hydrolysis --> alcohol and COO- group (carboxylate, not alkoxide)

 

[kingo44]

Gas X =N02
Gas Y =O2
2Mg(NO3)2 = 2MgO + 4N02 +O2

mass of gas X (NO2) produced =4*(mr of NO2)=4(46)=184
mass of gas Y (O2) produced =mr of O2=32

X/Y=184/32=5.75=1/0.174=5.75

answer = A

5.175 then wat

 

[Snowysangel]

How do u convert C2H5OH into C2H5Cl?

 

[kingo44]

how many of the compounds shown will react with aqueous sodium hydroxide to form the solution salt of carboxylic acid

 

[kingo44]

A h3C-0-C=0-CH2-CH3

 

[Zepudee]

help urGENT PLZZZZZZZZzView attachment 45080

mass of nitrogen in 14 g = 15/100 * 14 = 2.1
moles of nitrogen = 2.1/14 = 0.15
conc in 5 dm3 = 0.15/5 = 0.03 mol dm-3

 

[kingo44]

B H-0-C=0-CH2CH3