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Edexcel A2 Chemistry Exams -6CH04 (14th June) and 6CH05 (22nd June) Discussion Thread

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Reply 40
Avatar for samb1234
samb1234
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Original post by Tomasio
koh+c2h5cooh>>>>> c2h5cook + h2o


and how would the carboxylic salt interact with any h+ ions
Reply 41
Avatar for drj24
drj24
8
Has anyone finished unit 5 revision?
Reply 42
Avatar for Tomasio
Tomasio
2
Original post by samb1234
and how would the carboxylic salt interact with any h+ ions

reforms the oh and propanoic acid, so the [OH-]> [H+]
Reply 43
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samb1234
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13
Original post by Tomasio
reforms the oh and propanoic acid, so the [OH-]> [H+]

So if it is reacting with h+ ions it is therefore reducing tje conc of h+ ajd hence the ph is greater than 7
Hi guys - was just doing a paper and I have a question about a multiple choice question that I can't quite get my head around.

I tried to work out number of volume of carbon by 12/44 x 150 and then subtract this from 50cm3 to work out the volume of hydrogen?? Not really sure how to work out the question to be honest. Would really appreciate a clear solution! Thanks very much :biggrin:

Original post by Funky_Giraffe
Hi guys - was just doing a paper and I have a question about a multiple choice question that I can't quite get my head around.

I tried to work out number of volume of carbon by 12/44 x 150 and then subtract this from 50cm3 to work out the volume of hydrogen?? Not really sure how to work out the question to be honest. Would really appreciate a clear solution! Thanks very much :biggrin:



Is the answer B?
The ratio of the hydrocarbon to co2 is 1:3

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Original post by Neurology
Is the answer B?
The ratio of the hydrocarbon to co2 is 1:3

Posted from TSR Mobile


Yeah I got B as well for the same reason, as well as the fact that there are 4 lots of H2O left over.
Any idea on how to do this?

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1462178790370.jpg18.1KB
Original post by Neurology
Any idea on how to do this?

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is the answer D ?
Original post by Neurology
Is the answer B?
The ratio of the hydrocarbon to co2 is 1:3

Posted from TSR Mobile


Thank you, yes the answer is B. Not sure how you get it from knowing the ratio of hydrocarbon to CO2 produced though. Could you explain? :tongue:
Hi Everyone! How are you all doing? :smile:
How's prep coming along?
Reply 51
Avatar for samb1234
samb1234
OP
13
Original post by Funky_Giraffe
Thank you, yes the answer is B. Not sure how you get it from knowing the ratio of hydrocarbon to CO2 produced though. Could you explain? :tongue:


Well let's look at the equation. You should hopefully know that a hydrocarbon burns fully in oxygen to make co2 and water. So the equation would be:

AX + BO2 ----->CH2O +DCO2, where X is the unknown hydrocarbon and A, B, C and D are the numbers needed to balance the equation. We know that the volume of the gas is proportional to the number of moles of that gas, so if we let the coefficient of X be 1 then we know there are 5o2 and 3CO2 (as their volumes are 5 and 3 times that of the hydrocarbon respectively). So:

X + 5O2 ----> CH2O +3CO2.

We can now balance the oxygens, there are 10 oxygens on the LHS and 6 on the RHS, so there must be 4 waters:

X+5O2 ----> 4H2O +3CO2.

We can then just balance the equation to work out X, there are 3 Carbons on the RHS and 8 hydrogens and therefore x must be c3h8
Original post by samb1234
Well let's look at the equation. You should hopefully know that a hydrocarbon burns fully in oxygen to make co2 and water. So the equation would be:

AX + BO2 ----->CH2O +DCO2, where X is the unknown hydrocarbon and A, B, C and D are the numbers needed to balance the equation. We know that the volume of the gas is proportional to the number of moles of that gas, so if we let the coefficient of X be 1 then we know there are 5o2 and 3CO2 (as their volumes are 5 and 3 times that of the hydrocarbon respectively). So:

X + 5O2 ----> CH2O +3CO2.

We can now balance the oxygens, there are 10 oxygens on the LHS and 6 on the RHS, so there must be 4 waters:

X+5O2 ----> 4H2O +3CO2.

We can then just balance the equation to work out X, there are 3 Carbons on the RHS and 8 hydrogens and therefore x must be c3h8


Got it. Many thanks!
Have people started doing papers in exam conditions? How's everyone finding them? What kind of scores is everyone getting?
Original post by PlayerBB
is the answer D ?


The Answer is A

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Original post by Funky_Giraffe
Thank you, yes the answer is B. Not sure how you get it from knowing the ratio of hydrocarbon to CO2 produced though. Could you explain? :tongue:


Sorry I couldn't reply earlier. Was busy the entire day. Anyway I hope you understood from the reply provided by samb :smile:

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Original post by Neurology
The Answer is A

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That's so confusing!
Original post by PlayerBB
That's so confusing!


Try imagining/re-drawing the functional groups in the same rotation as the one given. They have been rotated to make it confusing.
Original post by dpoojaraa
Try imagining/re-drawing the functional groups in the same rotation as the one given. They have been rotated to make it confusing.


Thank you, it definitely made the question easier :smile:

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Original post by PlayerBB
Thank you, it definitely made the question easier :smile:

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No problem! Have you started doing full papers in timed conditions? I seem so intimidated whenever I try.

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