Sig Figs
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Sig Figs
When doing a problem that does not have any number values in the question but uses molar masses that extend to 4 sig figs, should you use the standard 3 sig figs in your answer or 4 sig figs coming from the molar masses?
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Re: Sig Figs
Even though the molar masses may have 4 sigfigs, I think you only need 3 sigfigs in your final answer. Hope that helps!
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Re: Sig Figs
If no values are specified in the problem, I would use the molar masses and round to 4 sig figs, since the periodic table allows for that precision. AKA whenever possible, it's best to be more precise.
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Re: Sig Figs
In addition, if we have to convert our calculated number of moles into grams, do not round off the number of moles. We only round to our number of significant figures at the very end of the problem. i.e. Say we are limited to 3 sig figs, and we calculated 3.45654 moles of Oxygen gas. We would multiply 3.45654 moles of Oxygen by 16.00 g/mol O2 to get 55.3g O2. DO NOT round the number of moles and multiply 3.46 moles of Oxygen by 16.00 g/mol O2. If we rounded the number of moles we would get 55.4g O2. This is known as round off error.
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Re: Sig Figs
Personally, I would try to let the calculator do all the work and then round at the very end, so you get the most accurate answer possible.
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Re: Sig Figs
throughout the problem, how many sig figs should we use when plugging things into our calculator? I've gotten different answers on some problems by rounding things that I plug in
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Re: Sig Figs
When in the middle of the problem, you should keep as many decimal places as possible, so that there is no rounding error. I usually keep 3 or 4 more decimals than I will need for my answer, just to be safe.
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Re: Sig Figs
I would round on your last step because the more you round the more your answer becomes inaccurate.
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