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Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: ruby92 on May 21, 2010, 08:10:42 pm

Title: chemistry paper 1
Post by: ruby92 on May 21, 2010, 08:10:42 pm
m/j 2002 p1
2 16 21 31
Title: Re: chemistry paper 1
Post by: Vin on May 21, 2010, 08:26:27 pm
LOL .. i tried the first one for fun and got it ! im doing igcse .. r u talking about the paper attached ?? :P

if yes thn

CH2O = 12 + 2 + 16
=30

Q2 is D

carbon .. 12/30 * 100 = 40%
oxygen .. 16/30 * 100 =53.3%

40% of 1.8 kg = 0.72 kg
53.3% of 1.8kg = 0.9594 kg
 
O2 = 0.9594 kg * 2 = 1.9188 kg


0.72kg + 1.9188 kg= 2.64 kg

..

Q 16. B
     
brine(when electro.)  ----> Sodium hydroxide + chlorine + hydrogen

2NaCl  + 2 H2O  ----> 2NaOH +  Cl2  + H2

so 1:1:2

21 & 31 .. never heard of such stuff !! 31. i kno option 1 is definitely not there 
..

pls. excuse if ive done the wrong paper :P



Title: Re: chemistry paper 1
Post by: unknown 101 on May 21, 2010, 09:04:34 pm
Quote from: ruby92 on May 21, 2010, 08:10:42 pm
m/j 2002 p1
2 16 21 31

Q2:

so the carbohydrate must be oxidised
Equation : CH2O + O2 ----> CO2 + H2O  ( already balanced )

find mr of carbohydrate and carbon dioxide

CH2O = 30
CO2 = 44

change these 2 values into kg by dividing with 1000
this ill give u:

0.03 and 0.044
so.. if 1.8 kg is eaten per day ( cross multiply):  0.044 x 1.8 / 0.03 = 2.64 kg


Q16:

answer is B
electrolysis of brine ( conc. aq. NaCl )

overall equation = 2Nacl + 2H2O -----> 2NaOH + H2 + Cl2 (balanced)



Q21: answer is C ( i will post a photo later on showing you how)



Q31:
answer is C ( 2 & 3 ) because

option 1 : is ethane and  ethene

normal formula for ethane is C2H6
and for ethene its C2H4

if u simplfy both of them then for ethane it will be CH3 and for ethene it will be CH2
and thats not the same

option 2 : ethene ( C2H4 ) and cyclohexane ( C6H12 )
simplify and u will get for ethene ( CH2 ) and for cyclohexane ( CH2 )

its the same so option 2 is right

option 3 : is cyclohexane ( C6H12 )  and oct-1-ene ( C8H16)
simplfy both and u will get for cyclohexane ( CH2 ) and for oct-1-ene ( CH2 )

its the same so option 3 is also right

so... answer is C

hope this helped... :)
Title: Re: chemistry paper 1
Post by: unknown 101 on May 21, 2010, 09:36:33 pm
photo is attached, hope u understand, and im sorry if i have bad handwriting lool :P
Title: Re: chemistry paper 1
Post by: princess12 on May 21, 2010, 09:39:42 pm
it is for which IGCSE,GCE-OLEVEL,AS,ALEVEL
 ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ???
Title: Re: chemistry paper 1
Post by: unknown 101 on May 21, 2010, 09:45:51 pm
Quote from: princess12 on May 21, 2010, 09:39:42 pm
it is for which IGCSE,GCE-OLEVEL,AS,ALEVEL
 ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ???

its for AS chemistry! :) i hope so!
Title: Re: chemistry paper 1
Post by: Vin on May 21, 2010, 10:20:06 pm
Quote from: unknown 101 on May 21, 2010, 09:36:33 pm
photo is attached, hope u understand, and im sorry if i have bad handwriting lool :P


oh ok now i know what the ques meant ..  ;D