Determining how many sig figs to use

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KaleenaJezycki_1I
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Determining how many sig figs to use

Postby KaleenaJezycki_1I » Tue Oct 01, 2019 11:18 am

Hi! I understand sig figs well, but am looking to clarify how many sig fig places you should go to the if the word problem doesn't directly state.

If my decimal answer came out to 4.978 do I round to 5.000 or 4.98 or so on?

Is it based on the number in the problem that has the lowest decimal place? Ex. 2.1 g of Na mixes with 3.18g of Cl ........
When I solve what the problem is asking, would my final answer have one decimal place or two?

Hope this makes sense! Thank you (:

Cynthia Gong 1L
Posts: 51
Joined: Fri Aug 09, 2019 12:15 am

Re: Determining how many sig figs to use

Postby Cynthia Gong 1L » Tue Oct 01, 2019 11:34 am

Typically your answer would contain the least amount of sig figs that is present in the question. Since in the example the number 2.1 has the least amount of sig figs of 2, your solution would contain 2 sig figs. As a result I believe your decimal answer would be rounded to 5.0. Hopefully someone else can also verify!

Annie Chantasirivisal_4G
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Joined: Wed Sep 18, 2019 12:21 am

Re: Determining how many sig figs to use

Postby Annie Chantasirivisal_4G » Tue Oct 01, 2019 11:37 am

I'm also unsure of how to use sig figs when the word problem doesn't state a number, such as F.1 only showing a molecular model of Citral and asking for the percentage composition... not sure how the solution came up with 2 decimal places.

But regarding "Is it based on the number in the problem that has the lowest decimal place? Ex. 2.1 g of Na mixes with 3.18g of Cl ........
When I solve what the problem is asking, would my final answer have one decimal place or two?"
if numbers are in the word problem, during multiplication and division you would use the lowest number of sig figs, which would be 2 from 2.1 g of Na; your final answer wouldn't necessarily include the decimal if it is already a big number, like for example if you got 44.5, your answer would be 44 since 44.5 would be three sigfigs.

Malia Shitabata 1F
Posts: 127
Joined: Sat Aug 17, 2019 12:17 am

Re: Determining how many sig figs to use

Postby Malia Shitabata 1F » Tue Oct 01, 2019 1:52 pm

I think for mass percentage compositions it usually rounds to two decimal places. I'm not sure if there's an exact sig fig rule for that.


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