Significant figures and order of operations

[Collin Li]

Use the relative atomic mass given in the chem booklet(from the exam).

Either that, or if its a question that requires you to calculate the molar mass, then just use the appropriate number of s.f.

That's right. VCAA booklet always provides 1 decimal place (which is usually 3 significant figures, but can be 4 or 2, depending on the atomic mass).

[Synesthetic]

Just as a supplementary note, I am led to believe that VCAA accepts one significant figure either way of the desired value. At least, this is my experience - in the Atomic Absorption Spectroscopy question for this year's Mid-Year Exam (Chemistry), I got the Statement of Marks and I had NOT been deducted any marks from that question despite giving one too many significant figures. (If I'm wrong, *please* refute this!)

But obviously do not take my word for it and don't assume this is always the case - perhaps it depends on the paper's difficulty and other variables that may cause the marker to change his/her mind. Don't relax about significant figures just because I posted this, this is just FYI anecdotally.

[shinny]

I second orsel's view on this:

In VCAA exams, you only have to give the correct s.f. for 1 particular question where they'll say something along the lines of 'giving the final answer to the correct number of significant figures'. For the rest of the questions, you only have to give the answer to +/-1 digit of the 'correct' s.f.

But I can't really give evidence either. My main evidence is that I'm sure I've seen evidence for the sig fig rule, and I've also heard many times only the question with the 'please ensure your answer is to the correct number of significant figures' clause is marked for correct sig figs. However I wouldn't stress too much...simplest way; just always use the correct number of sig figs and not risk marks. It's really not that hard.

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Thanks for all your contributions everyone