## Molar Mass

Posts: 64
Joined: Fri Sep 28, 2018 12:27 am

### Molar Mass

When we're using the molar mass, should we estimate according to how many sig figs are in the problem or do we use the most accurate molar mass we have?

Ex. problem asks to gives 3.45 g. of carbon. Would we use 12.0 or 12.011 for the molar mass?

skyeblee2F
Posts: 62
Joined: Fri Sep 28, 2018 12:23 am

### Re: Molar Mass

I believe you always answer with 3 sig figs in it's scientific notation form. So if it's 1.201 * 10^(-1), then you would answer 12.01 for the molar mass.

Jonathan Omens 1K
Posts: 60
Joined: Fri Sep 28, 2018 12:15 am

### Re: Molar Mass

Use the most accurate molar mass given to you. If the periodic table you are using gives the molar mass of carbon as 12.011 g/mol, then use that.
Because the problem you gave an example of starts with 3.45g carbon (3 sig figs), the final result should be rounded to 3 significant figures. In other words, only round to the correct number of significant figures at the end of the problem.

Jonathan Cheng 3C
Posts: 30
Joined: Fri Sep 28, 2018 12:23 am
Been upvoted: 1 time

### Re: Molar Mass

Use the molar mass provided regardless of the significant figures. Only round the final answer to the correct amount of significant figures needed.

WilliamNguyen_4L
Posts: 65
Joined: Fri Sep 28, 2018 12:28 am

### Re: Molar Mass

I would use the most accurate value for molar mass in calculations and then round the final answer according to sig figs.

Fionna Shue 4L
Posts: 59
Joined: Fri Sep 28, 2018 12:18 am

### Re: Molar Mass

Use the value that is given in the periodic table that you are referring to and then round the final answer to the correct number of sig figs.