sig fig calculations

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Austin Clack
Posts: 29
Joined: Fri Sep 28, 2018 12:17 am

sig fig calculations

Postby Austin Clack » Fri Oct 12, 2018 3:41 pm

In high school chemistry I was taught that there are a variety of sig fig rules about calculating. For example, when doing addition or subtraction with measured values, the answer should have the same precision as the least precise measurement. Does anyone know if these rules still apply, or if our sig figs should just be based on those we're given in the question?

whitney_2C
Posts: 74
Joined: Fri Sep 28, 2018 12:28 am

Re: sig fig calculations

Postby whitney_2C » Fri Oct 12, 2018 3:58 pm

Yes, there are a variety of sig fig rules for calculations based off of division, addition, subtraction, and even for when you're taking logarithms (I think we'll do that in our acid base unit). If you're answering a question, your sig figs should be based off of your least precise measurement, that is to say, the given number in the question with the least number of sig figs for multiplication and division. However, for addition and subtraction your answer should be based off of the least amount of decimal places of the given values.

Ex: 31.145 - 2.12 = 29.025 but with sig figs your final answer is 29.03 not 29.0 since 2.12 has the least amount of decimal places (2)

Ex: 29.3 x 3.454 = 101.2022 but with sig figs your final answer is 101 since 29.3 has the least number of sig figs (3)

Lavelle also has a whole page on sig figs on his website! https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/EVERYTHING_YOU_WANTED_TO_KNOW_ABOUT_SF.pdf

Karina Jiayu Xu 4E
Posts: 58
Joined: Fri Sep 28, 2018 12:29 am

Re: sig fig calculations

Postby Karina Jiayu Xu 4E » Sat Oct 13, 2018 8:59 pm

Do you use the least number of significant digits from the given values for your answer?

Ariel Cheng 2I
Posts: 67
Joined: Fri Sep 28, 2018 12:29 am

Re: sig fig calculations

Postby Ariel Cheng 2I » Sat Oct 13, 2018 10:02 pm

For addition and subtraction, you use the least number of decimal points from the given values and for multiplication, you use the least number of sig figs from the given values.


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