ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: Matt-Ong on June 11, 2011, 07:30:00 pm

Title: Significant Figures?
Post by: Matt-Ong on June 11, 2011, 07:30:00 pm

So I was wondering that in questions, do you use the result that you got on your calculator or do you round it up to the correct sig figs for the next calculation.

Eg.
1)
a) 
Mass of Barium = 0.00021g
Moles of Barium Reacted = 0.21x10^-3 / 137.3  = 1.52949x10^-6 or 1.5x10^-6mol

So in the subsequent question, would you use 1.52949x10^-6 as your calculations or would you use 1.5x10^-6?

Title: Re: Significant Figures?
Post by: Greatness on June 11, 2011, 07:34:16 pm

It doesnt really matter as long as you leave your answer to sig figs. Although it's good to remain consistent. I like to grab the answer that i got i.e. the one that's not rounded to use for future calculations.

Title: Re: Significant Figures?
Post by: Matt-Ong on June 11, 2011, 07:36:36 pm

But in the 2009 Assessment Report, Question 10c, they used 1.5 instead of 1.529, and that made my final answer become 0.20mg. The answer given was 0.19mg.
So would this still be considered right?

Title: Re: Significant Figures?
Post by: schnappy on June 11, 2011, 07:39:42 pm

I've always been told that for subsequent calculations use as many decimal places you have, but in stated answers you sig fig it up.

Seams conter intuitive, but if you wrote out a large equation with pronumerals for the subsequent question you can see where the issue is. with using shortened numbers early on.