Jessica Tran_3K
Posts: 50
Joined: Thu Jul 25, 2019 12:17 am

Hi,

If we are asked to perform calculations (ie calculate mass % composition or molar mass) in a problem that doesn't give us numbers to work with, how would we know how many sig figs to include in our answer? What's a good rule of thumb to go by in this case?

Thanks!

Callum Guo 1H
Posts: 134
Joined: Fri Aug 02, 2019 12:15 am
Been upvoted: 1 time

### Re: Sig Figs in Answer

I would probably do 3 but that might not be right.

KHowe_1D
Posts: 103
Joined: Thu Jul 25, 2019 12:15 am
Been upvoted: 1 time

### Re: Sig Figs in Answer

If you weren't given ANY numbers to work with, I would simply round to 3 decimals. That's what I normally do. But remember not to round until the final answer.

There are a few resources that are on the website that include the rules for sig figs.

Megan Ngai- 3B
Posts: 50
Joined: Fri Aug 09, 2019 12:17 am

### Re: Sig Figs in Answer

For calculating mass % I usually do four sig figs ex: 56.78%
For molar mass I would do four sig figs after the decimal points ex; 12.3456

jisulee1C
Posts: 149
Joined: Thu Jul 25, 2019 12:17 am

### Re: Sig Figs in Answer

I would do to the hundredths place if it was a percentage or to 4 sig figs if there was no numbers given in the problem.

ranqiao1e
Posts: 51
Joined: Sat Sep 14, 2019 12:15 am

### Re: Sig Figs in Answer

Usually I would do three, but I think 4 works better for certain questions. I would leave no more than 4.

Leyna Dang 2H
Posts: 104
Joined: Thu Jul 25, 2019 12:17 am

### Re: Sig Figs in Answer

Because it's not specified, I think using 3 or 4 sig figs would be fine. Having 4 sig figs would make your answer a bit more accurate, but I think using 3 would also be completely fine.

AChoudhry_1L
Posts: 55
Joined: Sat Sep 07, 2019 12:17 am

### Re: Sig Figs in Answer

In terms of percentage calculations, I would leave 4 sig figs such as 56.41%, however in answers with decimals I would leave at least have three digits after the decimal, such as 0.379 or 15.255. Remember to keep as many digits as possible when calculating and only round when you get your final answer. This will help make sure that your answer is as accurate as possible.

Nicholas Chin 1G
Posts: 100
Joined: Thu Jul 11, 2019 12:17 am

### Re: Sig Figs in Answer

Although it's usually good practice to go to 4 for mass percentage composition, it actually depends on how many sig figs you have for the mass of elements you use. For example, if you use 12.01 for Carbon, you have 4. But if you use 12.0107, you have 6.