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### Significant figures when there are constants

Posted: Tue Oct 01, 2019 10:44 am
Say you have the compound C10H16O and you want to find the mass percentage. I know that you need to multiply 10x12.01 to get the mass of C. In this case, would I need to use 2 sig figs or can I just use 1.201 as the mass of carbon?

(I don't need help finding mass percent composition after I've found the mass of carbon I just need some help determining the significant figures)

### Re: Significant figures when there are constants

Posted: Tue Oct 01, 2019 12:13 pm
You would use 12.01 and have four significant figures in your answer. The 10 is an exact number and can be written as 10.00.

### Re: Significant figures when there are constants

Posted: Tue Oct 01, 2019 12:50 pm
Actually, exact numbers do not impact the number of significant figures in a calculation. In the example you provided, the 10 is exact and does not affect the problem's significant figures. Similarly, when you divide by 1000 to convert from mL to L, that 1000 will not affect significant figures because it is exact. Only approximations will affect significant figures.

### Re: Significant figures when there are constants

Posted: Wed Oct 02, 2019 7:06 pm
In this case, would you round all throughout the problem or continue with exact numbers and round at the end to get 4 sig figs?