Chemistry Help

Are there different formats for writing the formulae maybe? Wikipedia seems to agree with the numbers = number of atoms theory.

Both are perfectly acceptable, and both will yield the same end result.

<-- Chemistry graduate
 
writing an equation with 0.5 oxygen molecules is wrong

no its not, your not saying you've got .5 of a molecule of oxygen your talking about the number of moles.

I must have written the formula of the petrol down wrong and have redone the calculation and got 2444g CO2.

cheers for your help
 
Both are perfectly acceptable, and both will yield the same end result.

<-- Chemistry graduate

ok so can you answer this please

2 C8H18 + 25 O2 = 18 H2O + 16 CO2

is it acceptable to write it as

C8H18 + 12.5 O2 = 9H20 + 8 CO2

apparently disco says using 0.5 is acceptable i say it isnt???
 
ok so can you answer this please

2 C8H18 + 25 O2 = 18 H2O + 16 CO2

is it acceptable to write it as

C8H18 + 12.5 O2 = 9H20 + 8 CO2

apparently disco says using 0.5 is acceptable i say it isnt???

Yes, it's exactly the same. The numbers can either refer to moles or atoms, but in the end it's entirely irrelevant because the end result will be identical whichever equation is used, and whether you are using atoms or moles

Conventionally, if you're using it to refer to atoms/molecules, you use integers only, but for a predictive result (which is the thing that matters) both equations yield exactly the same result in use, and as such any preference is just that, a preference, well either that or an instruction.

We had lecturers who used both conventions depending on their personal preference.
 
Well that's the thing. It's a form of notation. Both are valid with justification.

I can define real (i.e. not necessarily integer) values to indicate a part of a mol of said molecule. Then, with that understood, we can write 9.5 H2 or 12.5 O2, or even 3.1415 Cl2.

Equally, I could say that the notation refers to whole molecules and thus we are restricted to integer values. In that case, 12.5 O2 would make no sense, as we have not defined what .5 of an O2 molecule is.


So, platinum, you're right..but then so is collister. I believe at higher level, though, it is generally accepted that they refer to relative moles because it works for however you think of it.
 
Well that's the thing. It's a form of notation. Both are valid with justification.

I can define real (i.e. not necessarily integer) values to indicate a part of a mol of said molecule. Then, with that understood, we can write 9.5 H2 or 12.5 O2, or even 3.1415 Cl2.

Equally, I could say that the notation refers to whole molecules and thus we are restricted to integer values. In that case, 12.5 O2 would make no sense, as we have not defined what .5 of an O2 molecule is.

This is pretty much spot on from my experience.
 
Hmm, I'm pretty sure I didn't do it in Higher Chemistry, and I thought A levels were a notch down from Highers.

Perhaps educational standards are actually increasing, despite what the papers say.

Good luck with the question, sorry I can't help. The only thing that comes to mind about school chemistry is that those metal sharpeners burn great.

I dont think they are. For the A2 chemistry i started last week they have taken out 4 mechanisms for benzene alone. My teacher says theyve taken some of the harder topics out of AQA A2 chemistry. Its still bloody hard!!! A2 = second year of a levels btw :).
 
chemisty? sounds more like maths to me.

my sister had some homework like that. She had to wordsearch math terms..... this was for maths :confused:
 
no its not, your not saying you've got .5 of a molecule of oxygen your talking about the number of moles.

I must have written the formula of the petrol down wrong and have redone the calculation and got 2444g CO2.

cheers for your help

I assume you fixed the molecular mass of C8H12 if you got that answer? You've written in the OP that it's 6.58mol but 750/108 is 6.95 :p.

The Halk - I think this is in the SYS/AH course. I definitely did this in high school but couldn't say if it was 5th or 6th year. You're right that AH directly replaced SYS.
 
I want to use c8h18 by the way, which is petrol, not c8h12 which isn't
my answer finally came out to 2315.8 which is for the c8h18 by the way
 
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