CHEMISTRY COMMUNITY

Posted: **Sat Dec 07, 2013 5:52 pm**

Always keep sufficient significant figures such that when rounding at the end the answer would be the same even if all digits had been retained in each step throughout the calculation.

Textbooks, solutions manuals, etc., often do this to minimize the amount of text (numbers) printed (but should have correct sig fig at the end).

Clearly if an answer will have 2 sig fig there is no need to keep 8 sig fig for each step, 4 sig fig would be sufficient to avoid round-off error at the end.

Posted: **Sat Oct 11, 2014 1:27 pm**

Will we be penalized for putting extra significant figures?

Posted: **Wed Oct 15, 2014 1:40 am**

I think we will because you can't get make up extra significant figures. We have to get our answer from what data is available to us.

Posted: **Wed Sep 30, 2015 3:07 pm**

Do you know if the problems will specifically tell us how many significant figures to use?

Posted: **Wed Sep 30, 2015 5:08 pm**

Can we just round off to the smallest amount of sig figs in the given numbers in the problem? Generally that's what I do (it's normally 3-4 sig figs), but I'm not sure if that's what he wants.

Posted: **Wed Sep 30, 2015 7:11 pm**

I'm pretty sure that's what he's interested in, using the lowest number of significant figures for the given numbers.

So if a problem gives 2.06 g of Carbon and 1.001 g of Nitrogen, you'd use 3 significant figures in your final answer as your Carbon quantity only has 3 sig figs despite your Nitrogen quantity having 4 sig figs.

Posted: **Wed Sep 30, 2015 10:10 pm**

If there is a multistep problem, do we maintain four significant figures per step, even for the following step? For example, if part A requires an answer with only four significant figures (example: 1.178), and part B uses that answer to solve for another variable, should we use 1.178 or the extended answer (example: 1.1783485)?
Also, if we wait until the end of the problem to apply significant figures (keeping the calculated answer and not rounding per mathematical operation), will we be marked off even if we show our work and the answer is off by ~0.1?

Posted: **Thu Oct 01, 2015 9:18 am**

Michelle Dela Rosa 1G wrote:If there is a multistep problem, do we maintain four significant figures per step, even for the following step? For example, if part A requires an answer with only four significant figures (example: 1.178), and part B uses that answer to solve for another variable, should we use 1.178 or the extended answer (example: 1.1783485)?
Also, if we wait until the end of the problem to apply significant figures (keeping the calculated answer and not rounding per mathematical operation), will we be marked off even if we show our work and the answer is off by ~0.1?

I have the exact same question. But from the discussion section I had yesterday, the practice problems that we did (which we were given three sig figs) maintained the three sig figs and the end of every calculation. So I would say for part B of your question should use 1.178.
But if I am mistaken, please let me know.

Posted: **Fri Oct 02, 2015 2:33 pm**

SigFigs are so simple they get confusing, I am just going to stick with the right amount, and if I am skeptical just go with less. My TA said that you can't add precision, but you can make it less precise.

Posted: **Fri Oct 02, 2015 4:13 pm**

Evamae Bayudan 1B wrote:Will we be penalized for putting extra significant figures?

Yes. You'll lose a point because you are making it seem like you have more accuracy than you actually do.

Posted: **Fri Oct 02, 2015 4:15 pm**

Jordanmjones13 wrote:Do you know if the problems will specifically tell us how many significant figures to use?

Evamae Bayudan 1B wrote:Will we be penalized for putting extra significant figures?

No. Your answer should have the same number of sigfigs as the number in the question with the lowest number of sigfigs

Posted: **Fri Oct 02, 2015 4:40 pm**

If we are calculating values using only constants, such as the wavelength of light emitted when an electron jumps from energy level n=4 to n=2, how many sig-figs should we use? Will we be using a sheet for constants and equations during exams (and thus should we follow the amount of sig-figs given there)?

Posted: **Sat Oct 03, 2015 11:10 am**

You will have to give your final answer with same number of significant figures as given in the question. Also all the equations and values will be given to you with the formulae.

Posted: **Sun Oct 04, 2015 7:10 pm**

When trying to figure out the sig. fig. of the final answer, do we take into account the sig. fig. of constants? I vaguely remember that my teacher for AP Chemistry said that we do not need to consider the sig. fig of constants (like Avogadro's number or speed of light) when we are determining the sig. fig. of our answer because there are slight variations to the constants. For example, the book uses 2.99 x 10^8 m*s^-1 but during the lecture Lavelle used 3 x 10^8 m*s^-1. The first number has three sig. figs. and the latter number has one. So, do we take constants into account when determining the sig. fig. for our final answer?

Posted: **Mon Oct 05, 2015 12:50 am**

I believe that when you are working with constants that are exact (or approximated down to specific number like 3 x 10^8m*s^-1) they are not counted when determining the number of significant figures. Contrarily, when the constants are not exact you should aim to have a larger quantity of significant figures in the constants than that of the data you collected.

Posted: **Sat Oct 10, 2015 8:53 pm**

So I've been wondering, what's so important about sigfigs? why does it matter how many numbers we leave after the decimal place?

Posted: **Sun Oct 11, 2015 12:17 am**

The purpose of using significant figures is to make sure that the answer you calculated isn't more precise than the number(s) you started with. If one rounds off numbers too soon, errors in calculations may occur, and significant margins of error can affect data collection. Also, the number of significant figures tells the reader what degree of precision you used in making measurements. Precision can be limited by the instrument used to make measurements. For example, if you have a 12 inch ruler and are measuring a flat object, it wouldn't make sense to list the measurement as 10.479412 inches. Sometimes, being too precise doesn't make sense, especially if someone is repeating an experiment to check your results.

Posted: **Sun Oct 11, 2015 3:46 am**

Are we supposed to have the correct sig figs for each step or just the final answer?

Thanks!

Posted: **Sun Oct 11, 2015 4:39 pm**

Samantha Rundle 4L wrote:Are we supposed to have the correct sig figs for each step or just the final answer?

Thanks!

Only the final answer requires the correct number of significant figures but for quizzes there are only a certain amount of points you can lose for significant figures. In others words you do not lose a point every time your sig figs are incorrect on an answer. I was told by a TA there are only so many points awarded for this and it is better to understand the concepts and calculations and then implement your sig fig knowledge

Posted: **Tue Sep 27, 2016 11:19 am**

Since the number of sig figs only matters in our final answer, is there a range of correct responses when it comes to free response? I'm assuming that some people will round differently throughout the process of finding an answer which can lead to varied answers.

Posted: **Tue Sep 27, 2016 11:57 am**

I provide all students with the same constants, equations, and periodic table.
Therefore all students should have the same answer if sig-fig and round-off are done correctly.

Posted: **Wed Sep 28, 2016 1:22 pm**

So if we are off by one sig fig, for instance, will the whole problem be counted incorrect?

Thank you!

Posted: **Wed Sep 28, 2016 4:32 pm**

CenCen wrote:So I've been wondering, what's so important about sigfigs? why does it matter how many numbers we leave after the decimal place?

Significant figures are important in the answer to a chemistry problem so that our answer is as precise as it can be from the information given to us. If we do not round or round too much, the answer we get doesn't correspond to the information we were given. Even though it is important to be accurate with your answer, it is also important to be precise, which can be done by making sure that our answer only has as many digits as is permitted from the given quantities.

Posted: **Thu Sep 29, 2016 9:54 am**

Michelle Dela Rosa 1D wrote:If there is a multistep problem, do we maintain four significant figures per step, even for the following step? For example, if part A requires an answer with only four significant figures (example: 1.178), and part B uses that answer to solve for another variable, should we use 1.178 or the extended answer (example: 1.1783485)?
Also, if we wait until the end of the problem to apply significant figures (keeping the calculated answer and not rounding per mathematical operation), will we be marked off even if we show our work and the answer is off by ~0.1?

In order to make the final answer more precise, I think we are supposed to hold off on applying sig figs until the final answer. If you round too early, you run the risk of having a final answer that is extremely off and not within the acceptable range. Instead, you should keep track of the sig figs in your scratch work but simply plug the whole problem into your calculator using the exact numbers and only use the sig figs that you wrote down on the side to determine the number of sig figs necessary in the final answer.

Posted: **Thu Sep 29, 2016 9:37 pm**

Does it matter how many significant figures there are after the decimal while adding, multiplying, dividing, etc. ? (or does the number of significant figures of the result matter only?)

Posted: **Fri Sep 30, 2016 10:38 am**

104822659 wrote:Does it matter how many significant figures there are after the decimal while adding, multiplying, dividing, etc. ? (or does the number of significant figures of the result matter only?)

Like the post above, a general rule I've always followed is to only round/determine sig figs for the answer because otherwise, your calculations will be off. So yes, the number of sig figs of the result only really matters.

Posted: **Fri Oct 07, 2016 3:39 pm**

Do constants play a role in the significant figures an answer should have?

Posted: **Fri Oct 07, 2016 4:37 pm**

Should we wait to round sig figs until the end of a calculation or round throughout?

Posted: **Fri Oct 07, 2016 4:42 pm**

Grant Menke 1C wrote:Should we wait to round sig figs until the end of a calculation or round throughout?

Generally, we are supposed to wait to round sig figs until we are at the end of all calculations for a problem. Otherwise if we round throughout calculations, our final answers will most likely be innaccurate.

Posted: **Fri Oct 07, 2016 10:17 pm**

michaeljwilson3 wrote:Do constants play a role in the significant figures an answer should have?

From what I've seen, I don't think constants affect amount of sig figs in the final answer.

Posted: **Fri Oct 07, 2016 10:58 pm**

Evamae Bayudan 1B wrote:Will we be penalized for putting extra significant figures?

I'm not sure if we will be penalized, but my TA told me that the most amount of points you'll be penalized is four points.

Posted: **Sat Oct 08, 2016 2:10 pm**

If a problem requires us to use both multiplication/division and addition/subtraction, which rule do we follow?

Posted: **Sat Oct 08, 2016 6:25 pm**

You have to use both. For example, (2.34+3.45)/1.5 = , use the addition/subtraction rule for (2.34+3.45), which gives you 3 sig fig and use multiplication/division rule for the next step, which gives the final answer with 2 sig fig.

Posted: **Sun Oct 09, 2016 8:54 pm**

For testing purposes, is there a difference between writing 1.8 x 10^-2 and 0.018? I know they're synonymous, but I've seen both used in the textbook and workbook so I was wondering if there is a preference for either when it comes to giving a final answer.

Posted: **Sun Oct 09, 2016 9:03 pm**

Josephine_Tang_3A wrote:For testing purposes, is there a difference between writing 1.8 x 10^-2 and 0.018? I know they're synonymous, but I've seen both used in the textbook and workbook so I was wondering if there is a preference for either when it comes to giving a final answer.

I would use 1.8 x 10^-2 because it is in scientific notation. But I don't think that you will be marked off if you use .018

Posted: **Mon Oct 10, 2016 5:50 pm**

Chem_Mod wrote:You have to use both. For example, (2.34+3.45)/1.5 = , use the addition/subtraction rule for (2.34+3.45), which gives you 3 sig fig and use multiplication/division rule for the next step, which gives the final answer with 2 sig fig.

I thought that we were supposed to keep as many digits as we could throughout the problem, and then only use sig fig rules for the final answer? Do we have to use sig fig rules for EVERY step???

Posted: **Mon Oct 10, 2016 9:37 pm**

Ariana, I believe that only the final answer has to have the correct number of sig figs and you use exact calculations throughout the problem to make sure your answer is accurate, but anyone feel free to correct me if I'm wrong.

Posted: **Thu Oct 13, 2016 1:31 am**

Yes, you will be penalized for having the wrong number of sig figs - you can lose up to 2 points on this upcoming quiz (which is 5%). I screwed this up big time.

Posted: **Sun Jul 02, 2017 10:23 pm**

So does that mean if the question uses 3 sig figs, we use 4 sig figs throughout the calculations, then round up (or down), will we get points of for being inconsistent? Do we have to maintain sig fig numbers when we can easily round up/down?

Posted: **Mon Oct 02, 2017 3:48 pm**

During the calculations I would just keep a long string of numbers after the decimal until I come to the answer and then apply sig fig rules to get 3 sig figs cuz 4 sig figs might not be enough to avoid round off error. I'm not sure what's meant by "inconsistent." As long as you avoid round off error by keeping many decimal places and end up with the correct number of sig figs, I don't think you'd get points off.

Sorry if I misunderstood your question and feel free to correct me if I'm wrong ^^'

Posted: **Mon Oct 02, 2017 10:39 pm**

I haven't seen anyone talk about this or maybe I missed the post, but on Lavelle's website there is a Sig Fig review document posted under the Text and Exam Schedule and the Solution Manual Errors link that helped me review Sig Figs!

Posted: **Mon Oct 02, 2017 11:39 pm**

A good way to ensure you have the correct number of sig figs is to convert each value to scientific notation. Therefore, if you were given the number 0.0020, you should write it as 2.0*10^-3. It is thus clearer that this number has 2 significant figures.

Posted: **Tue Oct 03, 2017 2:40 pm**

I believe we use a sig fig rule each time we do a calculation. For addition/ subtraction, the number of decimal places in the answer should have the smallest number of decimal places from the number being added/ subtracted. Example: 112.2+60.23= 172.4 . For multiplication/ division, the number with the least sig figs that is being multiplied/ divided will determine the number of sig figs in the answer. Example: 525.5/5.54=94.9 .

Posted: **Tue Oct 03, 2017 10:20 pm**

Hi,
when there are numerous instances in a problem when multiplication/division is needed, can we just find the final answer and do the sig fig in the end after all the multiplication?
Also, is a problem with both addition and multiplication different because you have to recount the sig figs after you add and after you multiply?

Posted: **Tue Oct 03, 2017 10:22 pm**

when finding the molar mass in the periodic table, how many sig figs do we use?

Posted: **Tue Oct 03, 2017 10:25 pm**

Timothy Kim 1F wrote:when finding the molar mass in the periodic table, how many sig figs do we use?

I usually use one more than the lowest sig fig in the question. i.e. How many moles of oxygen are there in 10.8 g of water? I would use the molar masses oxygen and hydrogen to the hundreths decimal place, but I think if you have time, the more exact the better!

Posted: **Tue Oct 03, 2017 10:34 pm**

Timothy Kim 1F wrote:Hi,
when there are numerous instances in a problem when multiplication/division is needed, can we just find the final answer and do the sig fig in the end after all the multiplication?
Also, is a problem with both addition and multiplication different because you have to recount the sig figs after you add and after you multiply?

When doing the problem, I don't think that you're supposed to round until the very end. After you find the answer, I think you do sig figs. Also for problems with both addition/subtraction & multiplication/division, you do sig figs in as you complete each operation.

Posted: **Tue Oct 03, 2017 10:36 pm**

LinaLi2E wrote:When trying to figure out the sig. fig. of the final answer, do we take into account the sig. fig. of constants? I vaguely remember that my teacher for AP Chemistry said that we do not need to consider the sig. fig of constants (like Avogadro's number or speed of light) when we are determining the sig. fig. of our answer because there are slight variations to the constants. For example, the book uses 2.99 x 10^8 m*s^-1 but during the lecture Lavelle used 3 x 10^8 m*s^-1. The first number has three sig. figs. and the latter number has one. So, do we take constants into account when determining the sig. fig. for our final answer?

I think we do need to take into consideration the sig figs for numers like 2.99 x 10^8 m/s or Avogadro's number; however, I believe constants when using dimensional analysis will not be taken into account. For example, when converting from 8.64 kilograms to grams (by multiplying kg by 1000), I don't think your answer reduces to 1 sig fig (9000 g) just because you multiplied by the constant 1000, which has 1 sig fig.

Posted: **Tue Oct 03, 2017 10:49 pm**

Jordanmjones13 wrote:Do you know if the problems will specifically tell us how many significant figures to use?

No. With the numbers that are given, you should know how many sig figs to use. But when using molecular mass, the best number is 3-4 sig figs. When in doubt, use 3 sig figs. Other than that, always apply the subtraction/addition/multiplication/division rules. Hope this helps!

Posted: **Wed Oct 04, 2017 4:31 pm**

JamesAntonios 1J wrote:
Jordanmjones13 wrote:Do you know if the problems will specifically tell us how many significant figures to use?

No. With the numbers that are given, you should know how many sig figs to use. But when using molecular mass, the best number is 3-4 sig figs. When in doubt, use 3 sig figs. Other than that, always apply the subtraction/addition/multiplication/division rules. Hope this helps!

What are the subtraction/addition/multiplication/division rules for sig figs? I understand the concept of using the numbers given but don't know what you're referring to with the "rules"

Posted: **Wed Oct 04, 2017 11:11 pm**

Jordanmjones13 wrote:
What are the subtraction/addition/multiplication/division rules for sig figs? I understand the concept of using the numbers given but don't know what you're referring to with the "rules"

For multiplication and division, the rule is to end up with an answer with sig figs equivalent to the sig figs of the numbers being multiplied and you always use the lesser number of sig figs. For example, if you are doing .50(2 sig figs) x .6(1 sig fig) your answer will have 1 sig fig.

For addition and subtraction it's different. When you add and subtract, take notice of how many sig figs are to the right of the decimal place. Your answer will end up having the lesser amount of numbers behind the decimal point. For example, in 5.678+6.5 your answer will only go up to the tenths place.

The wording is a little confusing but I hope the examples help

Posted: **Fri Oct 06, 2017 9:42 am**

Remember that when looking at sig figs for numbers that have decimals, the placement of the ZEROES is important!

For example:

0.05 has 1 sig fig.
0.0500 has 3 sig figs.

In decimals, zeroes placed after a digit in the decimal places are significant, while those placed before are not.

An alternate way to check this is to write the number in scientific notation.

0.05 is 5 x 10^-2 --> 1 sig fig
0.0500 is 5.00 x 10^-2 --> 3 sig figs.

Hope this helped!

Posted: **Fri Oct 06, 2017 9:43 am**

Remember that when looking at sig figs for numbers that have decimals, the placement of the ZEROES is important!

For example:

0.05 has 1 sig fig.
0.0500 has 3 sig figs.

In decimals, zeroes placed after a digit in the decimal places are significant, while those placed before are not.

An alternate way to check this is to write the number in scientific notation.

0.05 is 5 x 10^-2 --> 1 sig fig
0.0500 is 5.00 x 10^-2 --> 3 sig figs.

Hope this helped!

Posted: **Fri Oct 06, 2017 2:10 pm**

Are we suppose to round to sig figs at every step of the problem? In response to a question in my lecture (lecture 3) Dr. Lavelle said to only round to sig figs at the end of the problem.

Posted: **Fri Oct 06, 2017 4:39 pm**

On the test on 10/6/17, I had trouble allotting enough time to answer all the questions and I believe it was mostly as a result of me taking my time thinking about what significant figures I should be using throughout my intermittent calculations. Are significant figures a crucial part to the test or am I able to cut down on the amount of time I'm focusing on sigfigs? I'm looking for ways I can be more efficient on the test so I can allot enough time for each question, any additional tips either?

Posted: **Sat Oct 07, 2017 6:45 pm**

What was the penalty for wrong significant figures on the test last Friday (10/06/17)?

Posted: **Sat Oct 07, 2017 8:17 pm**

In a multistep problem, should we use sig figs with every step, or only when it comes to the final answer? Will we be penalized if we use more than the amount of sig figs in intermediate steps but have the correct amount for the final answer?

Posted: **Sat Oct 07, 2017 10:53 pm**

804899546 wrote:In a multistep problem, should we use sig figs with every step, or only when it comes to the final answer? Will we be penalized if we use more than the amount of sig figs in intermediate steps but have the correct amount for the final answer?

I am pretty sure we are supposed to only use sig figs in the final answer, to be as accurate as possible with intermediate steps. So you probably will not be penalized for not rounding during intermediate steps! :)

Posted: **Sun Oct 08, 2017 12:25 pm**

nathansalce 3e wrote:On the test on 10/6/17, I had trouble allotting enough time to answer all the questions and I believe it was mostly as a result of me taking my time thinking about what significant figures I should be using throughout my intermittent calculations. Are significant figures a crucial part to the test or am I able to cut down on the amount of time I'm focusing on sigfigs? I'm looking for ways I can be more efficient on the test so I can allot enough time for each question, any additional tips either?

A tip for time management on the test is to skip to the problems you really know so that for the problems you struggle with, you'll know exactly how much time you have for them. As for sigfigs, don't round until calculating the answer for the whole problem. In multi-step problems, my TA said that you should use the rounded, correct sigfig answer of part a, for example, when solving for part b. Unfortunately, it seems that your final sigfig answer is crucial for the test, because he said that on the front of the test (I learned that the hard way too).

Posted: **Sun Oct 08, 2017 8:01 pm**

nathansalce 3e wrote:On the test on 10/6/17, I had trouble allotting enough time to answer all the questions and I believe it was mostly as a result of me taking my time thinking about what significant figures I should be using throughout my intermittent calculations. Are significant figures a crucial part to the test or am I able to cut down on the amount of time I'm focusing on sigfigs? I'm looking for ways I can be more efficient on the test so I can allot enough time for each question, any additional tips either?

I also had this problem I felt as is a lot of my time during the test was spent trying to ensure the accuracy of my answers by carrying out numbers to high decimal placements during the intermediate steps. How lenient are penalties when dealing with minor rounding errors in the final answer?

Posted: **Sun Oct 08, 2017 10:36 pm**

Kendall Schemmer 1I wrote:
JamesAntonios 1J wrote:
Jordanmjones13 wrote:Do you know if the problems will specifically tell us how many significant figures to use?

No. With the numbers that are given, you should know how many sig figs to use. But when using molecular mass, the best number is 3-4 sig figs. When in doubt, use 3 sig figs. Other than that, always apply the subtraction/addition/multiplication/division rules. Hope this helps!

What are the subtraction/addition/multiplication/division rules for sig figs? I understand the concept of using the numbers given but don't know what you're referring to with the "rules"

When adding/subtracting, your sig figs are the number of decimals in your answer is equal to the smallest number of decimal places in the data. When multiplying/dividing, your sig figs are the smallest number of sig figs in your data.

Posted: **Fri Apr 06, 2018 1:26 pm**

If a a question such as F.5 asks for the mass percentage composition, but does not specify any numbers that would give a basis for how many sig figs I need in my answer, do I just use the usual methods for rounding off even though there are not a certain number of sig figs specified to use? Also, what if my mass percentage composition does not add up to 100%?

Posted: **Fri Apr 06, 2018 1:43 pm**

Do we know how we will be graded with sig figs on the homework? I understand it would be good practice to make sure that we have the correct sig figs on the homework for the test, but when the TA's are grading the homeworks, will we be docked if we have not used the proper amount of sig figs?

Posted: **Sat Apr 07, 2018 8:58 pm**

I am wondering how many sig figs are we supposed to round off our answer to after getting the value from a calculator?

Posted: **Sun Apr 08, 2018 11:19 am**

The number of significant digits will depend on the starting number of significant digits and the mathematical operation you are carrying out.

Posted: **Tue Apr 10, 2018 7:44 pm**

This forum is very helpful!

Posted: **Sat Sep 29, 2018 11:03 am**

Jordanmjones13 wrote:Do you know if the problems will specifically tell us how many significant figures to use?

No, it is up to us to determine how many significant figures to use. Always use the least amount of significant figures that were given in a problem.

Posted: **Wed Oct 03, 2018 11:04 pm**

Do we have to be aware of sig figs for every single calculation we carry out? I'm confused as to whether we don't have to worry about them or not when calculating something like molar mass.

Posted: **Thu Oct 04, 2018 3:06 pm**

When finding the molar mass in the periodic table how many sig figs do we use?

Posted: **Thu Oct 04, 2018 3:07 pm**

Shuyi Yu 1B wrote:When finding the molar mass in the periodic table how many sig figs do we use?

We use the amount of sig figs given on the specific periodic table.

Posted: **Thu Oct 04, 2018 10:05 pm**

Should we maintain the amount of sig figs as determined by the periodic table that we're using or should it be determined by the problem (i.e. use the number with the least amount of sig figs)?

Posted: **Thu Oct 04, 2018 10:26 pm**

Milena Aragon 1B wrote:Should we maintain the amount of sig figs as determined by the periodic table that we're using or should it be determined by the problem (i.e. use the number with the least amount of sig figs)?

it mostly always is determined by the problem

Posted: **Thu Oct 04, 2018 10:27 pm**

When we are rounding, how can we determine how many sig figs we need to keep in the problem?

Posted: **Fri Oct 05, 2018 2:10 am**

How do significant figures work when the number is larger for instance if there was a problem that said find how many moles of hydrogen are in 2.00 kg of H. The answer is 1,984.127 but how do we know how many significant figures there are when you need more digits just to get back to 0 than were given in the initial problem?

Posted: **Fri Oct 05, 2018 3:34 pm**

angelagd3l wrote:When we are rounding, how can we determine how many sig figs we need to keep in the problem?

The final answer should have the same number of sig figs as the value given in the problem itself with the LEAST amount of sig figs.

Posted: **Fri Oct 05, 2018 3:48 pm**

Hi is it ok to not bother about significant figures in the beginning of calculations (by writing down more than the required sf.), and only round it to the correct number of sf. in the last equation?

Posted: **Fri Oct 05, 2018 3:54 pm**

Henry Dudley 1I wrote:How do significant figures work when the number is larger for instance if there was a problem that said find how many moles of hydrogen are in 2.00 kg of H. The answer is 1,984.127 but how do we know how many significant figures there are when you need more digits just to get back to 0 than were given in the initial problem?

I think you can use scientific notation to indicate the significant figure, like 1.98×10³ in this case to indicate 3s.f.

Posted: **Fri Oct 05, 2018 3:56 pm**

605122791 wrote:Hi is it ok to not bother about significant figures in the beginning of calculations (by writing down more than the required sf.), and only round it to the correct number of sf. in the last equation?

Yes, it should be okay to round off at the last step.

Posted: **Fri Oct 05, 2018 4:09 pm**

How many sig figs do we need to use from a periodic table? Is the tenths place ok?

Posted: **Sun Oct 07, 2018 3:11 pm**

I think when taking values from the period table it's safe to use 4 sig figs.

Posted: **Sun Oct 07, 2018 3:21 pm**

Can someone help me with a quick review of zeros in sig figs? I always get confused as to which zeros count as significant and which ones do not.

Posted: **Sun Oct 07, 2018 4:21 pm**

taywebb wrote:Can someone help me with a quick review of zeros in sig figs? I always get confused as to which zeros count as significant and which ones do not.

1. All non zero numbers are significant.
ex) 613 has 3 sig figs

2. Zeros located between non-zero digits are significant
ex) 5004 has 4 sig figs

3. Trailing zeros (those at the end) are significant only if the number contains a decimal point; otherwise
they are insignificant (they don’t count)
ex) 10000. has 5 sig figs but 10000 only has 1 sig fig

4. Zeros to left of the first nonzero digit are insignificant
ex) 0.052 has 2 sig figs

Posted: **Tue Oct 09, 2018 12:26 am**

Estelle Jung wrote:
taywebb wrote:Can someone help me with a quick review of zeros in sig figs? I always get confused as to which zeros count as significant and which ones do not.

1. All non zero numbers are significant.
ex) 613 has 3 sig figs

2. Zeros located between non-zero digits are significant
ex) 5004 has 4 sig figs

3. Trailing zeros (those at the end) are significant only if the number contains a decimal point; otherwise
they are insignificant (they don’t count)
ex) 10000. has 5 sig figs but 10000 only has 1 sig fig

4. Zeros to left of the first nonzero digit are insignificant
ex) 0.052 has 2 sig figs

This was a great refresher, thank you!

Posted: **Tue Oct 09, 2018 8:27 pm**

I heard of a rule about keeping different numbers of sig figs depends on doing multiplication or addition. Does someone know about this rule and maybe help me clarify it? Thank you!

Posted: **Fri Oct 12, 2018 9:44 pm**

When taking values from the periodic table (ex. for calculating molar mass), how many significant figures do you round to?

Posted: **Fri Oct 12, 2018 9:58 pm**

Yiwen Chen-3G wrote:I heard of a rule about keeping different numbers of sig figs depends on doing multiplication or addition. Does someone know about this rule and maybe help me clarify it? Thank you!

For addition/subtraction your answer has to be the same as the smallest number of decimal places from the data and with multiplication/division the sig figs in your result is the same as the smallest number of sig figs from the data. This can be found in Appendix 1C in the textbook if you want to read more into it!

Posted: **Sat Oct 13, 2018 3:03 pm**

Justin Le 2I wrote:I think we will because you can't get make up extra significant figures. We have to get our answer from what data is available to us.

If we get it wrong do you think we will still get partial credit for trying?

Posted: **Sun Oct 14, 2018 1:52 pm**

Jasmine Reddy DIS 1E wrote:When taking values from the periodic table (ex. for calculating molar mass), how many significant figures do you round to?

Try to not round answers until the very last step. I usually use the entire given value from the periodic table then round to the smallest number of significant figures used in my calculations.

Posted: **Sun Oct 14, 2018 1:54 pm**

Arlene Linares 3A wrote:
Justin Le 2I wrote:I think we will because you can't get make up extra significant figures. We have to get our answer from what data is available to us.

If we get it wrong do you think we will still get partial credit for trying?

I think we will as long as our answer is relatively close to the actual answer.

Posted: **Tue Nov 13, 2018 2:56 pm**

Lina Petrossian 3D wrote:
Arlene Linares 3A wrote:
Justin Le 2I wrote:I think we will because you can't get make up extra significant figures. We have to get our answer from what data is available to us.

If we get it wrong do you think we will still get partial credit for trying?

I think we will as long as our answer is relatively close to the actual answer.

Awesome thank you for the information.

Posted: **Sun Nov 25, 2018 5:34 pm**

You will still get a few points taken off if the significant figures are not correct.

Posted: **Sat Jun 29, 2019 3:46 pm**

Yes, it was stated in class that incorrect significant figures would lead to a deduction of 1 point from your answer. You only need to worry about them when writing your final answer though. When multiplying and dividing (so most of the problems) your answer must use the fewest number of significant figures that appear in your calculations.

Posted: **Mon Sep 30, 2019 10:08 am**

Does Dr. Lavelle prefer rounding or truncating digits for the final answer?

Posted: **Wed Oct 02, 2019 11:25 am**

Evamae Bayudan 1B wrote:Will we be penalized for putting extra significant figures?

I think we will be penalized since adding extra significant figures or removing them will result in an inaccurate response in the context of the question.

Posted: **Thu Oct 03, 2019 10:52 am**

is there a consistent rule of how many sig figs there should be? or does it depends on what the problem is asking for?

Posted: **Thu Oct 03, 2019 8:29 pm**

Sig Figs are confusing but shoutout to everyone in the replies for making it a little easier to understand.

Posted: **Thu Oct 03, 2019 8:34 pm**

melinak1 wrote:is there a consistent rule of how many sig figs there should be? or does it depends on what the problem is asking for?

The number of sig figs you need in your answer depends on how many sig figs are give in the numbers of the problem.

Posted: **Thu Oct 03, 2019 8:39 pm**

Jordanmjones13 wrote:Do you know if the problems will specifically tell us how many significant figures to use?

I don't think it will tell us, you will be left to figure it out by referring to the information given. There is a lot of good crash courses on how to count sig figs online. I hope this helps!

Posted: **Thu Oct 03, 2019 8:40 pm**

Lina Petrossian 1D wrote:
Jasmine Reddy DIS 1E wrote:When taking values from the periodic table (ex. for calculating molar mass), how many significant figures do you round to?

Try to not round answers until the very last step. I usually use the entire given value from the periodic table then round to the smallest number of significant figures used in my calculations.

Yeah! If you continually round throughout solving it can throw off your answer and its accuracy. Definitely try to avoid doing it if you can until the very end.

Posted: **Thu Oct 03, 2019 10:08 pm**

When in doubt about sig figs, pay attention to how many sig figs that the values given in the question have.

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