The Student Room Group

Chemistry ocr AS level question

The complete combustion of 0.0117mol of X produces 2.00x10^-3 m^3 of carbon dioxide gas, measured at 24.0 degrees and 101kPa.
Determine the molecular formula of X.

I'm really not sure how to tackle this question.

Thanks
(edited 7 years ago)

Scroll to see replies

Your question is far too vague. Please post the full question (with images if possible)
(edited 7 years ago)
Reply 2
image.jpg Haha I know, that's literally all it says though!
Original post by Farmerjj
image.jpg Haha I know, that's literally all it says though!


Show alkane X! That is crucial to the question!
Don't worry, some questions, especially ocr require you to look back at the previous information given haha.
(edited 7 years ago)
Original post by Farmerjj
image.jpg Haha I know, that's literally all it says though!


It's heptane.

Use PV = nRT for mol of CO2 produced and compare to mole of X burned
Reply 5
Original post by nwmyname
Show alkane X! That is crucial to the question!
Don't worry, some questions, especially ocr require you to look back at the previous information given haha.


Oh sorry forgot to put that top bit. 😊
Reply 6
Original post by TeachChemistry
It's heptane.

Use PV = nRT for mol of CO2 produced and compare to mole of X burned


Alright I'll try that cheers
Reply 7
Original post by TeachChemistry
It's heptane.

Use PV = nRT for mol of CO2 produced and compare to mole of X burned


I got 0.012 for the moles but how the heck did you get heptane from that?
Original post by Farmerjj
I got 0.012 for the moles but how the heck did you get heptane from that?


Post a picture of your working please.
Original post by TeachChemistry
Post a picture of your working please.


where is this question so I can find it online? is it a specimen paper?
Reply 10
image.jpg
Original post by TeachChemistry
Post a picture of your working please.
Reply 11
Original post by nwmyname
where is this question so I can find it online? is it a specimen paper?


It's the new OCR A depth in chemistry but I don't think this ones online
Original post by Farmerjj
image.jpg


You have not rearranged the equation properly AND you have not used the correct value for the volume.
Reply 13
image.jpg
Original post by TeachChemistry
You have not rearranged the equation properly AND you have not used the correct value for the volume.


Sorry here ya go
Original post by Farmerjj
image.jpg

Sorry here ya go


Now look at the ratio of the number of moles you just calculated and the number of moles given for X in the question.
Reply 15
Original post by TeachChemistry
Now look at the ratio of the number of moles you just calculated and the number of moles given for X in the question.


Oh I get it now man cheers 😄
There is a new paper?! What is this?! @TeachChemistry it would be the biggest favour in the world if you could put it up online please here on this post!
Original post by Farmerjj
Oh I get it now man cheers 😄

+1 and follow from me for an excellent question.
Original post by nwmyname
There is a new paper?! What is this?! @TeachChemistry it would be the biggest favour in the world if you could put it up online please here on this post!


No idea. I'm not the OP.
Original post by Farmerjj
The complete combustion of 0.0117mol of X produces 2.00x10^-3 m^3 of carbon dioxide gas, measured at 24.0 degrees and 101kPa.Determine the molecular formula of X.
I'm really not sure how to tackle this question.
Thanks


good revision website www.technocratnotes.com

and good revision apphttps://play.google.com/store/apps/d...s.app&hl=en_GB

can you add this to your originalpost please so that any new ppl to the thread see this. thanks

Quick Reply