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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Astrokel on September 24, 2008, 03:41:30 AM

Title: A level organic qn
Post by: Astrokel on September 24, 2008, 03:41:30 AM
hello,

i am stuck in this question as attached and i have no idea how to start. can anyone start me off with some hints or explanations?

my attempt: 2C6H5N + 33/2 O2 ---> 5H2O + 12CO2 + 2NO2 (+excess oxygen)
calcium chloride will remove the water, while KOH remove acidic gases nitrogen dioxide and carbon dioxide. So at point Q will left with excess oxygen while at P all the 4 products will be presence. Then isn't Mp/Mq  > 1 since mass at Mp is definitely larger due to all 4 products while at Q only excess oxygen, so answer will be D, but it is not.

thank you
Title: Re: A level organic qn
Post by: Borek on September 24, 2008, 04:37:28 AM
Think it over, you are on the wrong track.

They ask not about gases present, but about gases adsorbed. Just look at products and think where they will end.

Also note that they want you to assume that NO2 was not adsorbed. Honestly, I have no idea if it will react with KOH or not. For sure it not precursor of nitrate nor nitrite, but that's chemistry, strange things may happen.
Title: Re: A level organic qn
Post by: Astrokel on September 24, 2008, 04:56:03 AM
thanks for the response

Did i miss out something on the assumption of NO2 was not adsorbed, or is it because the reaction is unsure of????

looking at the products, the increase in vessel of Q will be due to CO2 and P will be H2O

Mr of CO2 = 44 , H2O = 18

Mp/Mq = (18x5)/(44x12) = 0.17

ye!!!!!!!!! thanks Borek for the guiding, thats the right answer ;D
Title: Re: A level organic qn
Post by: Borek on September 24, 2008, 07:31:35 AM
Did i miss out something on the assumption of NO2 was not adsorbed, or is it because the reaction is unsure of????

Results show that you have to assume it is not adsorbed (yes, I have solved the question before answering to check). Also, I don't remember reading or learning about NO2 reacting with bases; but first - I don't know everything, second - this is chemistry, doesn't matter what you think, what matters is what happens in the glass.
Title: Re: A level organic qn
Post by: Astrokel on September 24, 2008, 09:31:20 AM
thanks heaps!!  :)