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Chemistry: Post your doubts here!

RoyalPurple

RoyalPurple

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RoyalPurple

RoyalPurple

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papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_s13_qp_51.pdf

Q1 c (iv) and (vi)? please help :(
thanks.
 
roxylara

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Guys I need help in the practicals. How much time do I allocate if there's 3 questions. Like complete each experiment in 20 maximum 30 minutes and leave the rest for calculations? I really suck at moles but do the moles in the exam papers are they all really similar or same? I'd appreciate any tips :)
 
AbbbbY

AbbbbY

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NinjaInPyjamas said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_2.pdf

help with 5(b) and (c) iii please?
Click to expand...

Is this crazy co-incidence or what? I was hoping it'd be this question haha.

5b)

C4H8O2.

HCO2CH2CH2CH3
CH3CO2CH2CH3
CH3CH2CO2CH3
HCO2CH(CH3)2

Ofcourse, now any of them can be W X Y and Z.

c(i): Carbonyl group
(ii): Ketone is present
(iii) Reverse solve this question. Look. Since part c(ii) tells us it has a ketone group when oxidised, it has to be a secondary alcohol. See the esters you made. In the ones I made, the 4th one uses a secondary alcohol.

So, HOCH(CH3)2
 
A

Abdel Moniem

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AbbbbY said:
Umm, you do realize you've answered 24 here, right? :p
Thank you for you help :D

quote="Suchal Riaz, post: 745892, member: 15977"]there are two c=c so two moles of Br2 are required to react completely. and (separately) 2 mol of h2 are required.
Click to expand...

A!

This is a pretty simple question which idk why a lot of students have trouble answering.

Tackle it like this.

If the compound was an alkane and had no rings or double bonds, number of H atoms present = 2n+2 = 2(20)+2 = 42

Now, every time there're 2H less, you'll either have a double bond or a ring. The question states that there's one aldehyde (C=O) and 1 ring structure which has 1 C=C so this accounts for 6 missing Hydrogens, thereby leaving you with 8 missing Hydrogens.

8/2 = 4 Hydrogens in the aliphatic side chain.

However, total C=C are 5 because you have to include the C=C from the cyclohexene + cis formation hence A[/quote]
 
A

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roxylara said:
Guys I need help in the practicals. How much time do I allocate if there's 3 questions. Like complete each experiment in 20 maximum 30 minutes and leave the rest for calculations? I really suck at moles but do the moles in the exam papers are they all really similar or same? I'd appreciate any tips :)
Click to expand...
complete dependedt on the paper . My paper required 30 minutes per experiment but in some cases you may need to spend more time in the titration dividing time like 45-20-25 something cause they will give a shorter experiment with a longer one
 
N

NinjaInPyjamas

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AbbbbY said:
Is this crazy co-incidence or what? I was hoping it'd be this question haha.

5b)

C4H8O2.

HCO2CH2CH2CH3
CH3CO2CH2CH3
CH3CH2CO2CH3
HCO2CH(CH3)2

Ofcourse, now any of them can be W X Y and Z.

c(i): Carbonyl group
(ii): Ketone is present
(iii) Reverse solve this question. Look. Since part c(ii) tells us it has a ketone group when oxidised, it has to be a secondary alcohol. See the esters you made. In the ones I made, the 4th one uses a secondary alcohol.

So, HOCH(CH3)2
Click to expand...

perfect coincidence haha. thanks!
 
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