OCR AS prac_Reaction of Ethanoic acid + atmosphere?

Hey how did the practical go for everyone? Just wondering if anyone could tell me what ethanoic acid reacts with in the atmosphere + what does it form to give the impurity. I didn't have a clue, guessed it formed ethanol after reacting with oxygen.

Please reply drivin me mad, wana know the answer and can't find anythin on the net. :smile:

Reply 1

sssjay

i guessed at water =|

i didn't even know what i was going on about ughh.

most of my class but ethanol aswell so i think that's prolly the right answer?

blates failed my practical ):

Reply 2

jamesharrison

OP

Could be water as well, there's moisture in the atmosphere and carboxlic acids react with water. People at my school said CO2, don't know what that would form tho.

Reply 3

mubarak

I think i got the bit where it was a reaction with the atmosphere wrong, when it said what is the impurity, i put down water but i think it was supposed to be CO2.

With the last bit, when u had to say excess or not did u take moles of the Na-sumthing and CO2 and find it WAS in excess?

Reply 4

jamesharrison

OP

No, worked out moles of CH3COOH using mass/molar mass and the same for NaHCO3 then the ratio in the equation was 1:1, so moles of NaHCO3 should be equal to or more than CH3COOH and it wasn't. So not in excess. (i think lol)

Reply 5

snake

i worked out moles of sodium hydrogen carbonate and den worked out the mass dat needs to b used for the reaction.
the mass of what was required was less then the mass used derefore i sed it was in excess
is dat ryt

Reply 6

Shade

Also, i got half of this paper wrong, round it hard especially the way the questions were worded, very odd.. I think the answer to the atmosphere and ethanoic acid is evaporation (since carboxylic acid shows some water characteristic), seems the only logical response in my mind atm..

Reply 7

jamesharrison

OP

I thought you had to use the masses given in the question e.g

mass of NaHCO3 = 0.30g
mass of CH3COOH = 0.40g

Mr of NaHCO3 = 72 moles = 0.30/72 = 0.004
Mr of CH3COOH = 60 moles = 0.40/60 = 0.006

That gives you the moles involved in the reaction. Equation shows 1:1 ration so moles of NaHCO3 should be equal to or more than 0.006 for reaction to fully take place. That was my guess anyways. Hope that helps

Reply 8

Verted

I cant remember how I worked it out, but I found that there was an excess of NaHCO3. I'm probably wrong though, as Chemistry isnt really my strongest subject. I also thought that it was reacting with CO2 from the atmosphere, but again I cant be certain about it.

Anyone good enough at Chemistry to be able to shed some light with some definitive answers?

Reply 9

Mustardseed

1

I thought it couldn't be CO2 because I reasoned that it couldn't be acidic, since that would appear to give a higher % purity... :confused:

I think the answer they were looking for was water; our teacher referred to it as 'glacial ethanoic acid' which, on further research after the exam, I find is used to describe 'water-free' CH3COOH. Which is annoying, because I put water, and then crossed it out and wrote oxygen!

Reply 10

Funny Mann

Mustardseed

I thought it couldn't be CO2 because I reasoned that it couldn't be acidic, since that would appear to give a higher % purity... :confused:

I think the answer they were looking for was water; our teacher referred to it as 'glacial ethanoic acid' which, on further research after the exam, I find is used to describe 'water-free' CH3COOH. Which is annoying, because I put water, and then crossed it out and wrote oxygen!

I think it is like this:
Carboxylic acids are produced by oxidation of alcohols or aldehydes (by refluxing with excess potassium dichromate and acid). When this oxidation wasn't complete the carboxylic acid is impure like it was stated in the Practical, so it is going to react with the oxygen in the atmosphere.

I am not sure that this is right but it would make sense, wouldn't it???? :wink:

Reply 11

Mustardseed

1

I think that would imply that the reaction with the atmosphere made it purer, though, not less so... I don't know :biggrin:

Reply 12

Stobsy

I put water vapour down. I think that's right, but I'm not totally sure.

Reply 13

VAI2007

1

Lmao! I put CO2, I had absolutely no idea about that question!!

I got that it wasn't in excess because the moles where less than the moles of E.

Also what did everyone get for their % purity? and for their mean titre?

I got 98% (A tad high I know :frown:

) and 19.95cm3

Reply 14

arpeggio

12

VAI2007

Lmao! I put CO2, I had absolutely no idea about that question!!

I got that it wasn't in excess because the moles where less than the moles of E.

Also what did everyone get for their % purity? and for their mean titre?

I got 98% (A tad high I know :frown:

) and 19.95cm3

I got 40% and something different for the mean titre (can't remember exactly but I think it was twentysomething!)

I didn't like this paper. Too many stupid questions...

Edit: oops no the 40% was percentage yield, so I might be talking about a completely different question. Ignore me...

Reply 15

Mustardseed

1

I got 93.5% and 20.15 for the mean titre.

OCR AS prac_Reaction of Ethanoic acid + atmosphere?

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