Chemistry: How to decide how many significant figures to use?

hollingr

Looking through past papers, they seem to arbitrarily decide how many significant figures they want.. and often say nothing then take marks away for not having the "correct" number.

When they don't mention how many significant figures they want an answer in, how are we supposed to know how many to give? Do we just give the same significant figures as the data given in the question?

Stalin and rugby

Dude wtf? Don't mean to sound like a bellend here but wtf sort of a question is that?

You're a med hopeful cmon. Just give 10,15, 100 significant figures nobody cares.. Give excess you'll never be penalized.

hollingr

They take away marks if you give too many decimal places a lot of the time.

It just annoys me that they are so ambiguous about it and I don't have a teacher to moan to buddy! It's not the most important thing but I don't like the ambiguity over something which should be extremely simple and obvious.

Stalin and rugby

Yea I understand what you're saying. They never give the densities of the liquids too.

Good luck bro

Spattersonox

our teacher always said to go to two points. This is obviously not concrete. Doubt you'd be docked though

partyatmygaff

Generally speaking 2 decimal points (For your final answer) is good enough. If it's good enough for pharmaceutical analysis, it ought to be good enough for LC Chemistry.

finality

Do they deduct marks if you leave things to extra decimal places?

hollingr

If they specifically ask for nearest whole number or to one decimal place and you don't give what they ask for or round off incorrectly they definitely dock marks, I've seen it a good few times in past papers to try catch people out!

Slow Show

hollingr wrote: »

They take away marks if you give too many decimal places a lot of the time.

What?

EDIT: Well obviously if they're telling you to round it off, but do they deduct marks if there's no mention of rounding off in the question, which there rarely is from what I've seen.

hollingr

Guess it doesn't make any difference, I'll stick to the two decimal places unless q says otherwise.

I just got a bit unsure since sometimes they give the answers to one, two or 3 decimal places and don't give any method to the madness.

storm in a teacup this.. pay no mind. back to the important stuff like learning off the course, as if loosing 1 mark to significant figures is going to change much anyways, bigger fish to fry for me !