Sig Figs for Molar Mass

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Justin Nguyen 3E
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Sig Figs for Molar Mass

Postby Justin Nguyen 3E » Tue Oct 06, 2020 10:09 am

When performing calculations with Molar mass how many sig figs should we be using? Most calculations I've seen involving molar masses, such as with Carbon (12.01g/mol) and Hydrogen (1.008g/mol) seem to use 4 sig figs as the norm. Is it better to stick with 4 sig figs just to be safe or base it off given values?

Brianna Martilla 1C
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Re: Sig Figs for Molar Mass

Postby Brianna Martilla 1C » Tue Oct 06, 2020 10:11 am

I think we should use the most sig figs that are available when solving, then round the answer's sig figs to the number in the problem with the least sig figs.

Brian Bui 3H
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Re: Sig Figs for Molar Mass

Postby Brian Bui 3H » Tue Oct 06, 2020 10:56 am

I agree with the statement above! I don't believe there's any strict requirement to how many sig figs we need for molar mass. For example, I've been using 16.00 g/mol instead of 15.9994 g/mol for oxygen but have still been getting the correct answers. I think as long as you're not too far off it shouldn't matter much, but just make sure to wait until the very end of the problem to round.

Astha Sahoo 3I
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Re: Sig Figs for Molar Mass

Postby Astha Sahoo 3I » Tue Oct 06, 2020 11:03 am

I would recommend using four since then your answers perfectly line up with the textbook answers, since they use four, but if you don't mind being 0.01 or 0.02 off from the actual answer, you can just use two.

Darlene Lien 3E
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Re: Sig Figs for Molar Mass

Postby Darlene Lien 3E » Tue Oct 06, 2020 11:10 am

Personally, I've been using two decimal places as well for the molar masses, and my answer hasn't been off by too much. I think either should work. Hope this helps!

Julianna Shimabukuro 1D
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Re: Sig Figs for Molar Mass

Postby Julianna Shimabukuro 1D » Tue Oct 06, 2020 12:00 pm

Depending on how many sig figs you use from the molar mass, your answer may be off by only 0.01, but typically this is allowed since it's so close to the original answer, and answers will vary depending on rounding and sig figs. I have been using the whole molar mass that they give, but I don't think it should matter too much in your calculations as long as you use the correct amount of sig figs for your final answer.

Becca Nelson 3F
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Re: Sig Figs for Molar Mass

Postby Becca Nelson 3F » Tue Oct 06, 2020 12:05 pm

I tend to use one decimal point for Molar Mass values on the problems we have been doing. If the Molar Mass is need for a lab, I will use more decimal points to have the most precise data as I can for that value. I do not think there should be much variation in the values especially after sig figs are accounted for (most answers end up having at most 1 to 2 values after the decimal)

Tanya Nguyen 1B
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Re: Sig Figs for Molar Mass

Postby Tanya Nguyen 1B » Tue Oct 06, 2020 12:13 pm

When I am calculating I like to use the most amount of numbers given (usually around four to five significant figures) so that I can get the most accurate answer. Then I would round the answers to the smallest amount of significant figures, if not I would usually keep it around four to five figures, but it is personally up to you.

Inderpal Singh 2L
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Re: Sig Figs for Molar Mass

Postby Inderpal Singh 2L » Tue Oct 06, 2020 12:33 pm

Similar to the other responses above, I use the largest amount of numbers to increase my accuracy. But then I would round down to the smallest amount of sig figs given within the actual problem. This may require you to use scientific notation to clean up the numbers. I am not sure how important sig figs are compared to actually obtaining the correct answer.

Chinmayi Mutyala 3H
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Re: Sig Figs for Molar Mass

Postby Chinmayi Mutyala 3H » Thu Oct 08, 2020 1:12 pm

I would use as many as there is available in the beginning and then at the end, I would round to the number with the least significant figures which is probably going to be whatever number was given in the problem itself.

Lily Mohtashami
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Re: Sig Figs for Molar Mass

Postby Lily Mohtashami » Thu Oct 08, 2020 5:02 pm

I would use four significant figures because then my answers line up with that of the textbook. Also the more decimal places you use without rounding the more accurate your number will be. Then at the end you can round to the least number of significant figures that are in the problem.

David Jen 1J
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Re: Sig Figs for Molar Mass

Postby David Jen 1J » Thu Oct 08, 2020 10:17 pm

I use 4 sig figs most of the time

Jeremy Wei 2C
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Re: Sig Figs for Molar Mass

Postby Jeremy Wei 2C » Thu Oct 08, 2020 11:41 pm

Hi I normally would use 4 sig figs for the molar masses unless the problem includes specific molar masses (with different sig figs) for you to use.

Eric Cruz 2G
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Re: Sig Figs for Molar Mass

Postby Eric Cruz 2G » Fri Oct 09, 2020 1:07 am

Hi, as many people have emphasized, the significant figures of the molar mass doesn't matter too much. Of course, having it be too rounded would cause inaccuracy. However, this leads me to emphasize that you should determine the significant figures of your final answer based on the information provided in the problem and not by the significant figures of the molar mass. The molar mass # varies for each periodic table you look at, so it is best to rely on the given information provided. For instance, (theoretically) if you are given the grams of the reactants and it is 2.50 grams, and no other numerical information is given, then the amount of significant figures in your final answer would be 3. :)

Juliana Rosales 1H
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Re: Sig Figs for Molar Mass

Postby Juliana Rosales 1H » Fri Oct 09, 2020 8:47 am

Personally I use whatever value the sapling periodic table has, including all the values after the decimal point that it might include. Try not to round because that will make your final answer stray further from the actual answer. Only round at the end.


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