Page 1 of 1

### Does molar mass count for sig figs?

Posted: Thu Oct 03, 2019 12:44 am
Do the values of the molar masses we use for calculations affect the number of significant figures the answer contains?

### Re: Does molar mass count for sig figs?

Posted: Thu Oct 03, 2019 12:47 am
No, only the given values determine the number of sig figs the answer will ultimately have.

### Re: Does molar mass count for sig figs?

Posted: Thu Oct 03, 2019 12:50 am
I would keep the molar masses as precise as possible until you get your final calculation to prevent any rounding error. Then, determine the number of sig figs based on the smallest value given in the problem.

### Re: Does molar mass count for sig figs?

Posted: Thu Oct 03, 2019 12:54 am
It doesn't count for sig figs but I think Dr. Lavelle just likes to round it off (round 15.999 g/mol for O to 16) for lecture to make things simple. But definitely when doing calculations, try to keep all numbers and round off until the end.

### Re: Does molar mass count for sig figs?

Posted: Thu Oct 03, 2019 2:13 pm
The molar mass from the periodic table does not affect our calculations, but the molar mass we get from a question or from our calculations do affect our calculations.

### Re: Does molar mass count for sig figs?

Posted: Thu Oct 03, 2019 3:14 pm
Is there a certain periodic table that we need to use because I know that some periodic tables online the molar masses are rounded while the one in the textbook is more precise. Would the rounding affect any answers?

### Re: Does molar mass count for sig figs?

Posted: Thu Oct 03, 2019 4:51 pm
It's your final answer to a problem that counts for sig figs. However, to ensure that your final answer is accurate, I would keep the molar mass and other calculations in between in their longest form as evident on the periodic table and then use sig figs for your final answer.