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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: Nomvalt on May 11, 2010, 10:11:33 pm

Title: ethanol structure
Post by: Nomvalt on May 11, 2010, 10:11:33 pm

   H  H
   |  |
H-C-C-O-H
   |  |
   H  H

How is this diagram incorrect? I think it has something to do with drawing O-H straight instead of in an angle... drawing O-H in an angle instead of straight (as above).

Title: Re: ethanol structure
Post by: Edmund on May 11, 2010, 10:13:13 pm

Looks fine to me :P

Title: Re: ethanol structure
Post by: Nomvalt on May 11, 2010, 10:22:02 pm

   H  H    H
   |  |    /
H-C-C-O
   |  |
   H  H

If it helps, I think my teacher drew it like above or something like that (I didn't write down and this is coming from memory)...and I think he said it had to do with bonding and took time to tell us. I think he said it's true for all alcohols and is something to be careful about.

Title: Re: ethanol structure
Post by: chem-nerd on May 11, 2010, 11:02:03 pm

You would not be marked incorrect for drawing the bond straight. You would be marked incorrect if you didn't show the bond between O and H and it had asked you to 'show all bonds'.

A common mistake on exams is forgetting to add the Hydrogens/giving Carbon too many bonds/writing CH3, especially when you are in a rush.

Title: Re: ethanol structure
Post by: Martoman on May 12, 2010, 02:50:13 pm

If the examiner has had a bad day (divorce, car crash, insults for being a hairy bear) then they will want to take marks off if the carbon chain doesn't look "pretty", that is, it isn't zig zagging. I know this because last year a friend of mine lost 1 mark over this. But like significant figures and states, only one mark can be taken off the entire paper.

Title: Re: ethanol structure
Post by: akira88 on May 12, 2010, 03:42:18 pm

I hope they're not THAT petty to take off marks just because you draw it straight and not zig zaggy... I like drawing it straight because it doesn't look as messy :P

Title: Re: ethanol structure
Post by: m@tty on May 12, 2010, 04:09:25 pm

Do we have to draw the zig-zag structure? I thought it was perfectly acceptable to draw straight chains? At least that is what my teacher has alluded to(as well as what I remember from my textbook)....

Title: Re: ethanol structure
Post by: chem-nerd on May 12, 2010, 09:57:24 pm

Quote from: Martoman on May 12, 2010, 02:50:13 pm

If the examiner has had a bad day (divorce, car crash, insults for being a hairy bear) then they will want to take marks off if the carbon chain doesn't look "pretty", that is, it isn't zig zagging. I know this because last year a friend of mine lost 1 mark over this.

This is definitely NOT true. As long as your answer is legible it will get the mark.

I repeat, NOT true!

*EDIT - legible and correct

Title: Re: ethanol structure
Post by: Potter on May 12, 2010, 10:37:54 pm

Unless it states to show its molecular geometry I doubt it matters how you draw it.