Structural Formulas (1 Viewer)

[KeypadSDM]

I have been told by two different teachers what structural formulas are:

My Chem Tudor (Who is seriously sweet, yet about 80 years old) said the structural formula for ethane is:

CH3-CH3

However my chem teacher told me that the structural formula for ethane is:
H H
H-C-C-H
H H

Putting every single little line in (the redundant way, since they are identical and there is no ambiguity between them)

In an HSC chemistry test i put down CH3-CH3 and the teacher marked me wrong because that was "Condensed Structural" not "Structural".

Does anyone know what the BOS recognises as "Structural" Formulas? (Becuase i want to appeal for my rightful mark)

 

[KeypadSDM]

The second ethane molecule is a bit dodgy (it's hard to do on the net)

 

[kini mini]

Welcome to the forums Keypad

I think that your teacher is being a little fussy, but it's difficult to argue for the mark. Most people would understand structural formula to mean what your teacher has clearly taken it to mean, writing your second answer or using the more advanced skeleton model. IIRC textbooks also refer to what you wrote as a condensed structural formula, differentiating it from a structural formula.

So unfortunately i think that you don't have much of a chance of getting that mark back - but look at it this way, you've learned something useful at very little cost .

 

[KeypadSDM]

So true, the HSC Chemistry course isn't anything at all like real life.

I mean seriously -- there is NO and i mean NO difference at all between them. And instead of being the nice people and giving us marks for them, they go and destroy our confidence by saying "Although your answer may be correct, we will give you 0/1 for the fun of it".

My main argument is that nowhere on the syllabus does it ask us to differentiate between structural and condensed structural, no matter what a textbook may say. (Remember textbooks aren't the be all and end all).

And thankyou for the welcome.

 

[kini mini]

Originally posted by KeypadSDM

My main argument is that nowhere on the syllabus does it ask us to differentiate between structural and condensed structural, no matter what a textbook may say. (Remember textbooks aren't the be all and end all).

I don't know what the exact syllabus point is to do with structural formulae, it would be interesting to know. I mention textbooks because although they aren't the definitive guide to the course as you pointed out, I got the impression from teachers that the expectations of markers can be influenced by what they know is printed in popular texts . Some of them were markers too.

Remember that the HSC chemistry course is more of a course about chemistry than a course in chemistry - and since you're new I'll repeat my general exam advice....pretend you're writing for a pedantic wanker .

 

[McLake]

Just always be safe and right the whole thing out ...

 

[spice girl]

Go tell your teacher to get a life.

Alternatively, go tell her to join BOS and write exam papers along with all those other bunch of froot loops.

 

[KeypadSDM]

I think it's only because i prove her wrong on a regular basis...
I need 99.3, she knows it, and she just goes and gives me a big cross...

 

[Twintip]

Originally posted by McLake
Just always be safe and right the whole thing out ...

Exactly. Condensed structural formulas can be very dangerous when they just ask for a 'structural formula' in the HSC. My teacher is an HSC marker, and he was telling me that last year or the year before, one particular question had a mark dedicated to the correct structural representation of the OH group on a molecule.

"-OH" lost a mark, "-O-H" didn't.

Listen to your teacher. She knows what she's talking about. Like spice girl, I reckon it's a stupid convention and I know all the text books like using condensed structural formulae, especially for functional groups, but it's better to be safe than sorry.