Rounding up for Empirical Formulas?

[DominicMalilay 1F]

I was wondering what the usual cutoff point for rounding up empirical formulas is. For example, if the final moles of a compound containing C,H, and O are 2.67,2.67, and 1 you would multiply by 3, but what about numbers like 2.85,2.85, and 1, or any other variant for that matter.

[Nane Onanyan 1G]

Usually if I find that I am getting numbers around the "0.80" range, then I realize something might be wrong. Generally the problems are set up so we do not run into these issues. I usually go back and check my rounding if my numbers aren't in the "recognizable" decimal range (i.e. 0.99, 0.33, 0.67)

[Katherine_Douglas_1F]

You aren't necessarily wrong if you are getting numbers like .8 or .2. It just means you have to plug in different numbers until you find a whole-number multiple. for example, a number with .8 can be multiplied by 5 to equal 4

[Sedge Greenlee]

Echoing what Katherine said, generally, you shouldn't have to round. Try to avoid rounding in any steps of the problem to retain the highest accuracy of a final answer. That way, when you reach your final answer and you have .8 or .2, you know that it's not an issue with accuracy and instead you need to find a factor to multiply each number by to reach a set of whole numbers.

[reva_bajjuri]

If you are having trouble finding a factor to multipy a decimal by, you might want to try writing it as a fraction over 100, simplifying it, and multiplying all of your moles by the lowest common denominator.

[Yashvi Reddy 1H]

I'd like to confirm what Sedge wrote! I agree with that approach. Good luck!

[Keshav Patel 14B 2B]

Confirming what many other students have posted, but you should not round until the final answer, I typically use 4-5 numbers to the right of the decimal if they are present and then round once I get to my final answer according to what the question requires.

[Xavier Herrera 3H]

I think that Reva's approach would be the best when you are having trouble finding a number to multiply your empirical formula by. It will ensure that you are getting the lowest ratio of whole numbers for your formula. However, you would usually be fine just multiplying your formula by different numbers until you get values that are above the 0.9 range of certainty.

[Emma Strassner 1J]

Hi, I agree with what Xavier said about 0.9 being a good threshold for rounding up. I am wondering if the same could be said for rounding down? For example, if your answer ends in .01-0.1, is that close enough to round down?

[Carly_Lipschitz_3H]

Hi, I agree with what Xavier said about 0.9 being a good threshold for rounding up. I am wondering if the same could be said for rounding down? For example, if your answer ends in .01-0.1, is that close enough to round down?

Yes, I believe so. I agree with 0.9 being close enough to round up. By that rational a number from 0.01-0.1 is close enough to round down.

[Emma Strassner 1J]

Okay great, that makes sense! Thank you!