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Sig Figs when finding Mol

Posted: Wed Oct 03, 2018 1:01 pm
by Grace Kim 1J
Hi Everyone!
I was wondering if sig figs matter when finding the mol.

For Example (Module 1: #5)
Mol of C: 54. 82 g/12.01 g. mol^-1= 4.56 mol OR 4.564 mol?

Regardless of which one we use, I know that we would get the same answer in the end after dividing by the smallest number, but I was wondering if we would get docked points for not using sig figs when showing our work for calculating mols. Thanks!

Re: Sig Figs when finding Mol

Posted: Wed Oct 03, 2018 1:14 pm
by monikac4k
If the number of moles is the answer to the problem, you would want to round according to the number of sigfigs, which in this case seems to be 4 significant figures. However, if you are going to continue using the number in further calculations, you should continue using the longer version. According to my understanding, significant figures are most important in the final answer, not during the calculations.

Re: Sig Figs when finding Mol

Posted: Wed Oct 03, 2018 2:44 pm
by 705152867
As long as your work is shown to lead to the answer with the correct number of sig figs, I don't think getting points docked would be an issue :)

Re: Sig Figs when finding Mol

Posted: Wed Oct 03, 2018 10:33 pm
by KarlaArevalo2F
It's always best to use the most amount of sig figs when continuing a problem, but always refer to the sig fig rules (which is mostly using the least number of sig figs I believe) when writing the final answer.

Re: Sig Figs when finding Mol

Posted: Wed Oct 03, 2018 10:41 pm
by Srikar_Ramshetty 1K
A good rule to remember when dealing with significant figures, especially in division and multiplication problems, is that your answer cannot be more significant than the least significant value present in the equation. For example, if you divide 4.56 by 2.1 (i.e. 4.56/2.1), then your answer would be 2.2, rather than 2.17. This is because 2.1 contains only 2 significant figures and getting an answer that is more precise than one of the values in the calculation would detract from the answer's validity. The values you provided as an example both contain 4 significant figures, therefore, your answer should also contain the same amount of significant figures.

Hope this helped!
- Srikar Ramshetty