Chemistry: Post your doubts here!

[GCE As and a level]

Thanks, but maybe if I played less FIFA and tried studying in these 20 days I wouldn't have had such a problem

PLZ SAY WE** NOT I

 

[Suchal Riaz]

Never happen to me

in the paper 1 on pst we had to do three set of question each set had one 4 marks, on 7 marks and one 14 marks question.
it took me half hour to do one 14 marks question only. the paper was of 1.5 hours. this way i couldn't complete even 70% paper in time.
but in examination hall my fingers raced so much that i completed paper 10 minutes earlier.

 

[GCE As and a level]

How do you do it
Like i see you as a person who always studies and i can never do that i study for an hour take a break for like 3 hours

Same here

 

[ZaqZainab]

in the paper 1 on pst we had to do three set of question each set had one 4 marks, on 7 marks and one 14 marks question.
it took me half hour to do one 14 marks question only. the paper was of 1.5 hours. this way i couldn't complete even 70% paper in time.
but in examination hall my fingers raced so much that i completed paper 10 minutes earlier.

Woh thats cool
but its vise versa for me
I can comple a P1 in 40 minutes at home but 'Bio pape 1' took me 1 hour and still didnt get time to check i have got problem with nervousness in exam hall

 

[Suchal Riaz]

just to clarify I DON'T STUDY ALL THE TIME
i study about 2-3 hours now. and started studies 5 days ago. i just pretend to study all times to encourage my friends to study and to try to hide my intelligence as i need to behave ordinary among ordinary people to look ordinary.

 

[Suchal Riaz]

Woh thats cool
but its vise versa for me
I can comple a P1 in 40 minutes at home but 'Bio pape 1' took me 1 hour and still didnt get time to check i have got problem with nervousness in exam hall

i was talking about paper1 of PST not mcq papers. btw i when i started it took me more than 2 hours to do one paper1 of chemistry as i had to make a lot of diagrams of organic chemistry, write all the equations, do all the working. now with expeience it all takes place in head and only minute working has to be done on paper. now it takes 40 sec to complete an average question but if i am stuck i can take about 2 minutes to find the solution. practices makes a man(and women) perfect.

 

[ZaqZainab]

just to clarify I DON'T STUDY ALL THE TIME
i study about 2-3 hours now. and started studies 5 days ago. i just pretend to study all times to encourage my friends to study and to try to hide my intelligence as i need to behave ordinary among ordinary people to look ordinary.

Every one is ordinary its you who make your self different
I am ordinary but i am the one who made myself study less and so i am less intelligent "
you decide what you wanna become and you made it to intelligence while i here am too lazy to do so

 

[ZaqZainab]

i was talking about paper1 of PST not mcq papers. btw i when i started it took me more than 2 hours to do one paper1 of chemistry as i had to make a lot of diagrams of organic chemistry, write all the equations, do all the working. now with expeience it all takes place in head and only minute working has to be done on paper. now it takes 40 sec to complete an average question but if i am stuck i can take about 2 minutes to find the solution. practices makes a man(and women) perfect.

when did you start like 5 days ago?
I started My first proper paper 20 days ago

 

[Suchal Riaz]

Every one is ordinary its you who make your self different
I am ordinary but i am the one who made myself study less and so i am less intelligent "
you decide what you wanna become and you made it to intelligence while i here am too lazy to do so

if one person is good at something than other then he must be worst at other things than the others.
if i am good at something(actually everything other than sports) it means you people are better than me in other things.

 

[Suchal Riaz]

 

[randomcod]

please pelase make it a bit more specific.
I though enthalpy change = enthalpy change of products - enthalpy change of reactants?

 

[..sacrifice4Revenge..]

any tips for the last 10mcqs?

 

[..sacrifice4Revenge..]

please pelase make it a bit more specific.
I though enthalpy change = enthalpy change of products - enthalpy change of reactants?

for combustion data, its reactants-products

for formation, products-reactants

bond energy, Exo+Endo

 

[Zepudee]

s08qp1

Q6.
H2O(s) --> H2O(g)

Moles of H2O = mass of ice/Mr of H2O = 1/18= 0.0556

PV/nT (ideal gas) = PV/nT (H2O)
(1)(24)/(1)(298) = (1)V/(0.0556)(596)

V = 2.67 dm^3

Q26.
Increase in the 2 oxygen means that the 2 OH has been oxidized to 2 COOH groups.
The two OH must be primary alcohols. Since is an unbranched butanol, the OH groups are on carbon 1 and 4.

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.

Thank you

 

[ZaqZainab]

please pelase make it a bit more specific.
I though enthalpy change = enthalpy change of products - enthalpy change of reactants?

I have learned it in another way and its a whole new concept but if you wanna know it i will explain my way it works everytime

 

[Zepudee]

W.salam,
Mr(P) = 31
Mr(P2O5) = 2(31) + 5(16) = 142
In 100 g of fertiliser, there is 30.0% P2O5
That means mass of fertiliser is
= (100/30) * Mr(P2O5)
= (100/30) * 142
= 473.3 g

% of phosphorus in fertiliser is
= (2*31 / 473.3) * 100 [(2*31) because there are 2 atoms of P in one molecule of P2O5 ]
= 13.1 %
So, A is the answer!

how do you know is 100g? Or is it already a standard?

 

[Zepudee]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w03_qp_1.pdf

Need help on Q3, 2o, 27 ( isnt the tertiary alcohol will be resistant to oxidation? ) and 40 ( why 2 cant be seen after distillation? )

 

[DeViL gURl B)]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_11.pdf

Question 2 8, 24,27,
Help needed please!!

 

[Metanoia]

Video on Nov 2011 P11 uploaded

http://www.youtube.com/playlist?list=PL4Jmce8VJnNX-EKGH10S1O8HEK2elI72j

This is likely to be the final paper uploaded before your exams.

I will try to work on the rest of the papers (both A and O levels) for the next few months and upload them eventually.
But I must say its not likely to remain free access for the future batches.

I'll try to help out by answering questions in this thread until Jun 10. After which you guys can enjoy a good break.

 

[kingo44]

come on metanoia one more paper