Post by: /0 on December 16, 2008, 09:11:20 pm
"For multiplication and division, the result should have as many significant figures as the measured number with the smallest number of significant figures.
For addition and subtraction, the result should have as many decimal places as the measured number with the smallest number of decimal places."
So what do you do if you have something like 0.235(16.0303+23.5+9.059)? Do you take the result in the brackets to 1 decimal place, multiply by 0.235 then take the answer to the lowest amount of significant figures?
Post by: shinny on December 16, 2008, 09:16:29 pm
Post by: /0 on December 16, 2008, 09:18:59 pm
And congratulations on your vce results ;)
Post by: /0 on December 16, 2008, 09:31:19 pm
You are given
Do you have to write
Post by: shinny on December 16, 2008, 09:41:30 pm
Post by: cara.mel on December 16, 2008, 10:46:40 pm
I am fairly sure you do not need to know this. Only just to make your final answer to the one with the least amount of sig figs (and also to ignore the amount of sig figs in the molar mass even if it is the least accurate thing)
Post by: /0 on December 17, 2008, 06:00:23 am
10 tonnes = 10^7 grams, but how accurate would this actually be?
Post by: cara.mel on December 17, 2008, 07:46:02 am
This is because as you put it, 10 tonnes = 10,000,000g. You can not tell me that 10,000,000g has 8 sig figs in it, same deal to any other unit conversion (it would only have more than one sig fig if it was like 10.0 tonnes, in which case it is 3 sig figs)
Also that is what I could call a dodgy question and the author probably meant it to be 2 sig figs, I've never given an answer to 1 sig fig
Post by: /0 on December 17, 2008, 05:22:48 pm
Post by: Collin Li on December 17, 2008, 05:43:00 pm
Post by: orsel on December 17, 2008, 06:12:17 pm
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.
Though you should probably take this with a boulder of salt.
Post by: vcestar on December 17, 2008, 06:26:33 pm
Post by: cara.mel on December 17, 2008, 06:29:39 pm
IIRC:
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.
Though you should probably take this with a boulder of salt.
That post is mainly accurate.
They will mark sig figs on one question
They will mark states on one question (s,l,g,aq).
These are not indicated in the question stem which question they will be picking on for marking sig figs or states.
For every other question, you need to include sig figs/states but if they're not super accurate it's no big deal. In other words you need to be sensible and not give you answer like 3.253353456 because 'oh sig figs may not be marked here ^__^'
Post by: /0 on December 18, 2008, 03:11:07 pm
How many decimal places do you need to put molar masses to? In one of the solutions they have
Post by: orsel on December 18, 2008, 04:52:32 pm
Either that, or if its a question that requires you to calculate the molar mass, then just use the appropriate number of s.f.
Post by: Collin Li on December 19, 2008, 12:56:51 am
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).
Post by: Synesthetic on December 19, 2008, 09:56:25 am
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.
Post by: shinny on December 19, 2008, 01:00:23 pm
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
Post by: /0 on December 19, 2008, 02:44:26 pm