Which number determines sig figs of the answer?
Moderators: Chem_Mod, Chem_Admin

 Posts: 89
 Joined: Wed Sep 30, 2020 10:09 pm
Which number determines sig figs of the answer?
If a question with numbers such as 8.25 g/mol and 9.2 grams, would significant figures of the answer be determined by the greater number of sig figs in 8.25 or the smaller number in 9.2?
Re: Which number determines sig figs of the answer?
It depends on what operation you use. In the case of multiplying them, then the number of significant figures would be determined by the one with the smaller number of sig figs.

 Posts: 111
 Joined: Wed Sep 30, 2020 9:58 pm
Re: Which number determines sig figs of the answer?
When multiplying or dividing, the sig figs will be equal to the number of sig figs in the least precise measurement. When subtracting or adding, the the result should have the same number of decimal places as the least precise measurement.

 Posts: 85
 Joined: Wed Sep 30, 2020 9:52 pm
Re: Which number determines sig figs of the answer?
it depends on what operations you are using throughout the problem. for adding/subtracting, the # of sig figs in the answer is determined by the value that has the least amount of number AFTER the decimal point. however, for multiplication/division, the # of sig figs in the answer is determined by the value with the least amount of sig figs (so 9.2). usually if there is both addition/subtraction and multiplication/division in a problem, I was told that your best bet is to go with the value with the least amount of sig figs, especially if it was already given in the problem. hope that helps :)

 Posts: 122
 Joined: Wed Sep 30, 2020 9:51 pm
Re: Which number determines sig figs of the answer?
For this example, if multiplying or dividing, whatever the number with the smallest amount of significant figures will determine how many sig figs will be in your final answer.

 Posts: 99
 Joined: Wed Sep 30, 2020 10:03 pm
Re: Which number determines sig figs of the answer?
In chemistry, there are two sets of operations with different rules when it comes to significant figures. With multiplication/division, the resulting answer will depend on the value of the least amount of sig figs; in this case, two significant figures (9.2). With addition/division, the resulting answer will have the same number of decimal places as the original number with the fewest decimal place; in this case, one decimal place (9.2).

 Posts: 92
 Joined: Wed Sep 30, 2020 10:11 pm
Re: Which number determines sig figs of the answer?
Supporting what others have said, the number of sig figs depends. For multiplication and division, use the smallest number of overall sig figs. For addition and subtraction, you look at the smallest number of decimal places and

 Posts: 91
 Joined: Wed Sep 30, 2020 9:49 pm
Re: Which number determines sig figs of the answer?
Generally, you want to use the least precise measurement to determine how many sig figs your answer will have. When multiplying/dividing, your answer should have as many sig figs as the measurement given that has the least sig figs. When adding/subtracting, your answer should have as many decimal points as the measurement given that has the least sig figs. Remember not to round in between calculations in order to be as accurate as possible!

 Posts: 78
 Joined: Wed Sep 30, 2020 9:37 pm
Re: Which number determines sig figs of the answer?
Do you know where we can find the rules for the sig figs? Like a completed list that has them simplified?
Re: Which number determines sig figs of the answer?
Charisma Arreola 2L wrote:Do you know where we can find the rules for the sig figs? Like a completed list that has them simplified?
https://lavelle.chem.ucla.edu/wpconten ... OUT_SF.pdf This PDF is the one on Lavelle's website, and there's a few other resources there as well

 Posts: 86
 Joined: Wed Sep 30, 2020 9:41 pm
Re: Which number determines sig figs of the answer?
For addition/subtraction problems, your final answer may have no more significant figures to the right of the decimal than the LEAST number of significant figures in any decimal portion of any number in the problem. For multiplication/division, the LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer (you are now looking at the entire number, as opposed to just looking at the decimal portion you would normally look at for addition/substraction problems)

 Posts: 87
 Joined: Wed Sep 30, 2020 9:40 pm
Re: Which number determines sig figs of the answer?
For any operation, just think LEAST. For adding/subtracting, you look for the least number of sig figs to the right of the decimal. For multiplying/dividing, you go for the least amount of sig figs in general.

 Posts: 88
 Joined: Wed Sep 30, 2020 9:55 pm
 Been upvoted: 1 time
Re: Which number determines sig figs of the answer?
For example if it was the answer would be 58.4. If you were doing something like the answer would be
13.3
13.3
Re: Which number determines sig figs of the answer?
I think for addition or subtraction, the answer of the question should have equal number or less significant figures than the number with the least significant figures in the question. In the case of multiplication or division, the answer should have the same amount of significant figures with the number that has the least amount of significant figures.

 Posts: 85
 Joined: Wed Sep 30, 2020 9:48 pm
 Been upvoted: 1 time
Re: Which number determines sig figs of the answer?
I don't really know how to post a new topic but it is related to this forum anyway so I'm just gonna ask it here. If a problem asks you to do both multiplying/dividing and adding/subtracting, what sig fig rule do you follow?

 Posts: 106
 Joined: Wed Sep 30, 2020 9:35 pm
Re: Which number determines sig figs of the answer?
Usually, the number with the least amount of sig figs determines how many sig figs you can use.

 Posts: 140
 Joined: Wed Sep 30, 2020 10:02 pm
 Been upvoted: 2 times
Re: Which number determines sig figs of the answer?
Based on what I learned from my chem teacher in highschool, we usually just went with the smallest number given to us in the actual problem.

 Posts: 86
 Joined: Wed Sep 30, 2020 9:39 pm
Re: Which number determines sig figs of the answer?
Typically in cases of chemistry you will have some type of multiplication or division in your problem and as a result you will just use the smallest amount of sig figs in the givens as the amount in your answer. (but follow the rules others have given above if your problem happens to only include addition/subraction).

 Posts: 88
 Joined: Wed Sep 30, 2020 9:40 pm
Re: Which number determines sig figs of the answer?
When you are multiplying it is determined by the number with the least amount of significant digits.

 Posts: 82
 Joined: Wed Sep 30, 2020 9:31 pm
Re: Which number determines sig figs of the answer?
While I understand the procedure, why is it that being able to round to a significant figure important in chemistry?

 Posts: 86
 Joined: Wed Feb 19, 2020 12:15 am
Re: Which number determines sig figs of the answer?
The number with the least amount of figures determines the sig figs.

 Posts: 93
 Joined: Wed Sep 30, 2020 9:57 pm
Re: Which number determines sig figs of the answer?
This depends on the operation. When adding or subtracting, look for the value with the least amount of numbers in the decimal place. Your answer will have that same number of digits after the decimal point. For example, if you're subtracting 17.9236.6, your answer will be 11.3. Note the single value after the decimal place. If you're multiplying or dividing, your answer should have the same number of sig figs as the value with the least amount. For example, if you're multiplying 82.891 and .045, then your answer will be 3.7.

 Posts: 81
 Joined: Wed Sep 30, 2020 9:38 pm
Re: Which number determines sig figs of the answer?
In general, I was told that it is best to go with the least amount of sig figs in the problem. It does however depend on what operations you are using throughout the problem.

 Posts: 87
 Joined: Wed Sep 30, 2020 10:00 pm
Re: Which number determines sig figs of the answer?
It depends on the operation of course, however a rule of thumb I always used was to go by the number that had the least number of significant figures

 Posts: 91
 Joined: Wed Sep 30, 2020 10:07 pm
Re: Which number determines sig figs of the answer?
The significant figure depends on what the specific question is asking for, if the question specifically asks about moles then you would refer to the sig fig of the moles given and used throughout the problem.
Re: Which number determines sig figs of the answer?
What should be done if the smallest number in the problem has 1 sig fig, and the answer is something like 1432 g? Should we round to 1000 g since that would be 1 sig fig?
Re: Which number determines sig figs of the answer?
Adding and subtracting have the same rule, after getting your answer you want to use the significant figure of the number that has the least set of numbers after the decimal. When you are multiplying or dividing you want to use the number with the least amount of significant figures.
Return to “Significant Figures”
Who is online
Users browsing this forum: No registered users and 1 guest