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Chemistry: Post your doubts here!

AbbbbY

AbbbbY

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Mustafa Malik said:
Hello everyone
I am new to this part of Xtremepapers cuz i hv just finished my O levels n in these vacations i wanna study for A levels .Although i created a thread but there was no reply:(. Actually i need the name of the best books for chemistry A levels that most renown skools follow.
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I use Roger Norris. Very nice book.

Although, I'll suggest you don't use it yet.

www.chemguide.co.uk
It has every topic very nicely covered. In fact, I use this to understand whatever I get stuck up at.

Also, I'll suggest you use these holidays to do other things instead of studying for your A's. Trust me on this one. I'll suggest
-> An Internship
-> Learn other skills, a foreign language perhaps?
-> Indulge actively in sports, alternatively, take up gymming and keep up with it.
-> If you have even a remote interest in it, take up computer programming, even if it's at a small level
-> Learn to play a music instrument etc.
-> If you plan to apply to the US, and don't want to do any of the above, and want to study, study for the SATI and give it in October, way before everyone else will plan on giving it in your batch. This is particularly helpful because you can then give a retake in Jan after rigorous study again if the need be.

These holidays are the only ones in your life you can truly dedicate time to these things (save for SAT). Don't waste them studying for A Levels. You'll manage that during the next two years aswell. These holidays wont come back, and the ones after your AS/1st year of A Levels will be much tougher and you wont have time for half of that. College essays, personal statements, internships, coursework, where to apply what aptitude tests to take, social work etc etc etc. Too much crap. Trust me.

I regret wasting my O Level holidays sleeping and gaming. I wish I had spent just one hour a day at the gym and one hour a day learning French. Would be in a much different position right now. Glad I did the internship that I did, albeit reluctantly. I dearly wish I had started on the SAT on those holidays. There's nothing in it that an O Level student cant do. The Math is O Level, the English, you won't gain anything stepping even into the second year of A Levels.

I have a lot of regrets on O Level summer. I hope you don't!

Good luck!
 
h4rriet

h4rriet

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zackle09 said:
i used pV=nRT but im getting a weird answer :/
and for 30.... in esters doesn't the alcohol come on the right side tho?
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Make sure you use the correct units.
It doesn't necessarily have to be on the right or left side; it'll be on the side of the -CO2. For example, an ester will be like this: acid-CO2-alcohol, or alcohol-O2C-acid. The C of the CO2 will be part of the c. acid.
 
daredevil

daredevil

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Ahmedraza73 said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_11.pdf
Can anyone solve Q:11,15,16,17,20
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16: A
becz if all three of these elemts wen pput in that case do have lone electron pairs. but not all of them increase by 1. NO --> NO2 here N increases its ox state by 2.
20. D
just count all the double bonds (3) for pie bonds
then the single bonds. remember to count C-H bonds n -CH3 also bcz htat is a possible over look u might do. it will help if u mark with a pencil the bonds u have counted. also count one sigma bond for all the double bonds too bcz first a sigma bond is made and then a pie bond so they do have a sigma bond too. they are 25 in total.

don't know the others well enough to tell u sorry. :)
 
Ahmedraza73

Ahmedraza73

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daredevil said:
16: A
becz if all three of these elemts wen pput in that case do have lone electron pairs. but not all of them increase by 1. NO --> NO2 here N increases its ox state by 2.
20. D
just count all the double bonds (3) for pie bonds
then the single bonds. remember to count C-H bonds n -CH3 also bcz htat is a possible over look u might do. it will help if u mark with a pencil the bonds u have counted. also count one sigma bond for all the double bonds too bcz first a sigma bond is made and then a pie bond so they do have a sigma bond too. they are 25 in total.

don't know the others well enough to tell u sorry. :)
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not understand yet :(
 
Z

zackle09

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h4rriet said:
Make sure you use the correct units.
It doesn't necessarily have to be on the right or left side; it'll be on the side of the -CO2. For example, an ester will be like this: acid-CO2-alcohol, or alcohol-O2C-acid. The C of the CO2 will be part of the c. acid.
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yeah so in part D isnt that the acid after CO2 instead of the alcohol :/
 
h4rriet

h4rriet

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zackle09 said:
yeah so in part D isnt that the acid after CO2 instead of the alcohol :/
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D is: CH2CH2CO2(CH2)4CH3. C is: CH3(CH2)4CO2CH2CH3 The underlined parts are from the carboxylic acids. D's is propanoic acid and C's is hexanoic acid. In the question, we start of with hexanol, with is then oxidised to hexanal, and then to hexanoic acid.
 
Z

zackle09

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h4rriet said:
D is: CH2CH2CO2(CH2)4CH3. C is: CH3(CH2)4CO2CH2CH3 The underlined parts are from the carboxylic acids. D's is propanoic acid and C's is hexanoic acid. In the question, we start of with hexanol, with is then oxidised to hexanal, and then to hexanoic acid.
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so yeah they're saying that Y reacts with ethanol..and if Y is an hexanoic acid..shouldnt it have 6 Cs rather then 3
 
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