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ALL CIE CHEMISTRY DOUBTS HERE !!

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cs:
I have questions here, attached picture, i am sorry if anyone has answer this before, there are so many pages, i will try to look for it

Edit: found my answer for the second one in previous page, so left the 1st and 3rd one.. Thanks

$!$RatJumper$!$:

--- Quote from: moon on November 13, 2010, 04:25:56 pm ---pls I need help in Nov.06 Q9, 11 12 31, 32.
June 01 Q6,11,37
thanks for ur help. :) :)

--- End quote ---


--- Quote from: Deadly_king on November 14, 2010, 08:04:25 am ---Nov 06 p1

12. At low temperature, less molecules will have have reached activation energy to undergo the reaction. Hence the graph with lower peak is to be used.

Energy of such a graph is found on the x-axis. ;)

Hence answer is D


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Energy at lower temperatures mean we take the graph with the higher peak and not the lower. Thus the answer is C and not D

elemis:
@CS

For the 1st question :

500/24000 = 0.020833333333 moles of oxygen.

Using avogadro's constant : 0.020833333333 divided by 1/(6.02*1023)

gives an answer of 1.25 *10^22

elemis:
@CS

For the Second question :

 

Imagine there is 1 mole of N2O4 hence there must be 2 moles of NO2

Therefore the partial pressures of each gas are 1/3 (N2O4) and 2/3 for NO2

inputting these into the initial equation at the top gives 4/3

$!$RatJumper$!$:

--- Quote from: moon on November 15, 2010, 01:16:31 pm ---pls can u help in Nov.08 Q3,30,39 and Nov. 09 Varient 1 Q5,21,22,28,29,31. Thanx in advance.

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--- Quote from: Deadly_king on November 15, 2010, 02:21:38 pm ---Nov 08 p1

30. First you need to use the mass of the respective molecules given to find the number of moles of each.

No of moles = Mass / Mr

No of moles of ethanol : 30/46 = 0.652
No of moles of ethanoic acid : 30/60 = 0.50
Ratio of moles of ethanol to ethanoic acid was supposed to be 1:1. Hence we can deduce that ethanol is in excess. Only 0.5 mole of each reactant will react.

No of moles of ethyl ethanoate : 22/88 = 0.25.
Hence it can be noted that only 0.25 mole of ester is formed when 0.5 mole of reactants react together.

% Yield is therefore : 0.25/0.5 x 100 = 50%

Answer is C

39. From the information given above, you can note that for methane which contains only one carbon atom, ethane with two carbon atoms can be obtained as product. In other words the number of carbon atoms double.

So for propane which contains 3 carbon atoms, the resulting product may contain maximum 6 carbon atoms.

Hence we can reject the last suggestion leaving us with only 1 and 2 as potential answers.

Answer is B


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For Q39 why do we reject the last one? Doesnt it also have 6 carbon atoms?

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