Sig Fig Mistakes

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Jina Kwon
Posts: 65
Joined: Fri Aug 09, 2019 12:15 am

Sig Fig Mistakes

Postby Jina Kwon » Thu Oct 03, 2019 11:20 am

For significant figures, does it matter how many sig figs you choose to use? Will anyone care if you choose to use four sig figs rather than three as long as you're being consistent?

Isha_Maniyar_Dis2E
Posts: 71
Joined: Thu Jul 11, 2019 12:16 am

Re: Sig Fig Mistakes

Postby Isha_Maniyar_Dis2E » Thu Oct 03, 2019 11:26 am

For sig figs, it depends on the question. Typically, the sig figs of the given amount in the problem is the number of sig figs you use for your final answer. However, that's not always true.

So you shouldn't be using 3 sig figs for every single answer just for consistency; you have to look at the question and choose the sig figs accordingly.

Hope this helped!

alexfwang3g
Posts: 50
Joined: Thu Jul 11, 2019 12:16 am

Re: Sig Fig Mistakes

Postby alexfwang3g » Thu Oct 03, 2019 11:28 am

For multiplication/division, the result should have the same number of sig figs as the value that has the least number of sig figs which is being multiplied/divided.

For example, if you are multiplying a value with two sig figs and a value with three sig figs, then the result should have two sig figs as that is what the value with the least number of sig figs has.

As for addition/subtraction, the result should be rounded off to the least precise decimal point in the subtraction/addition equation.

For example, 140.22 - 110.1 would yield 30.12. But with the application of sig fig rules, the answer should be rounded off to 30.1 since the tenths decimal point is the least precise point shown in a comparison between 140.22 and 110.1.

Michelle Chan 1J
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Joined: Thu Jul 25, 2019 12:16 am

Re: Sig Fig Mistakes

Postby Michelle Chan 1J » Thu Oct 03, 2019 11:32 am

I agree with the post above. I remember from high school chem there were certain sig figs rules. For example, when multiplying or dividing, you answer with the least number of sig figs in the problem. For addition and subtraction, the answer can not contain more decimal places than the least precise value.

Audrie Chan-3B
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Joined: Thu Jul 25, 2019 12:17 am

Re: Sig Fig Mistakes

Postby Audrie Chan-3B » Thu Oct 03, 2019 11:50 am

Typically, you find the number with the smallest number of sig figs given in the problem and use that as a guidance as to how many sig figs you should have in your final answer!

Janet Nguy 2C
Posts: 74
Joined: Sat Aug 24, 2019 12:17 am

Re: Sig Fig Mistakes

Postby Janet Nguy 2C » Thu Oct 03, 2019 12:10 pm

^^I'm wondering the same thing; will we be docked points for sig fig mistakes?

Drake Choi_1I
Posts: 58
Joined: Sat Aug 17, 2019 12:15 am

Re: Sig Fig Mistakes

Postby Drake Choi_1I » Thu Oct 03, 2019 12:13 pm

Can someone please explain the sig fig rules regarding addition and subtraction as well as multiplication and division? I forget which one is about having the same amount of decimal places and which needs the same amount of sig figs. Thank you!

Letty Liu 2C
Posts: 67
Joined: Fri Aug 09, 2019 12:16 am

Re: Sig Fig Mistakes

Postby Letty Liu 2C » Thu Oct 03, 2019 2:13 pm

Should we round off the numbers as we calculate or leave them as is until the final answer?

Rohan Kubba Dis 4B
Posts: 50
Joined: Sat Aug 17, 2019 12:18 am

Re: Sig Fig Mistakes

Postby Rohan Kubba Dis 4B » Thu Oct 03, 2019 2:31 pm

The general idea for sig figs is that you are trying to be precise because your calculation is only as accurate as your least accurate measurement. For example for the hypothetical problem find moles of F- in 25.2kg of UF6, it is important to round your answer to three sig figs at the end. The reasoning for this is because the only numeric value they give us explicitly (yes you can deduce the molar mass), is 25.2 kg, we have to use this as our benchmark for sig figs as there are three numeric values present.

Sally Qiu 2E
Posts: 66
Joined: Fri Aug 30, 2019 12:18 am

Re: Sig Fig Mistakes

Postby Sally Qiu 2E » Thu Oct 03, 2019 2:41 pm

Letty Liu 1K wrote:Should we round off the numbers as we calculate or leave them as is until the final answer?
I was taught to not round as you calculate, as that would interfere with the accuracy of your final answer. Then, you can round and use the sig figs.

Madeline Phan 1E
Posts: 68
Joined: Sat Aug 17, 2019 12:18 am

Re: Sig Fig Mistakes

Postby Madeline Phan 1E » Thu Oct 03, 2019 3:13 pm

The number of sig figs you use should depend on the number with the least number of sigfigs given in the question. For example, if the problem gives you an amount like 3.2 grams and 4.56 grams, your answer should have 2 sigfigs since 3.2 grams only has 2 sigfigs.

cnguyen1k
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Joined: Wed Sep 18, 2019 12:20 am

Re: Sig Fig Mistakes

Postby cnguyen1k » Thu Oct 03, 2019 9:41 pm

I know this was already asked but if we don't use accurate sig figs will we lose points during exams?

Anna Chen 1K
Posts: 63
Joined: Thu Jul 25, 2019 12:18 am

Re: Sig Fig Mistakes

Postby Anna Chen 1K » Thu Oct 03, 2019 11:24 pm

When dealing with multiplication or division problems, the number of sig figs in your answer should equal the smallest number of sig figs in the given values. When dealing with addition and subtraction problems, the number of sig figs in your answer should equal the smallest number of decimal places in the given values.

Emil Velasco 1H
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Joined: Wed Nov 21, 2018 12:19 am

Re: Sig Fig Mistakes

Postby Emil Velasco 1H » Thu Oct 03, 2019 11:27 pm

I think you round the answer's sig fig to the smallest number at the calculation

Amir Bayat
Posts: 79
Joined: Sat Sep 07, 2019 12:16 am

Re: Sig Fig Mistakes

Postby Amir Bayat » Thu Oct 03, 2019 11:35 pm

In addition to this statement, during calculations it is best not to round as accuracy may be lost in the final answer. Therefore, it is best to round to the least amount of significant figures given to you in the exercise at the end for the answer (as stated below).

Madeline Phan 4H wrote:The number of sig figs you use should depend on the number with the least number of sigfigs given in the question. For example, if the problem gives you an amount like 3.2 grams and 4.56 grams, your answer should have 2 sigfigs since 3.2 grams only has 2 sigfigs.

chrischyu4a
Posts: 52
Joined: Thu Jul 25, 2019 12:16 am

Re: Sig Fig Mistakes

Postby chrischyu4a » Fri Oct 04, 2019 4:39 pm

One important thing to note is that when determining the number of sig figs to use in your final answer, you don't consider the amount of sig figs in constants such as Avogadro's number.

Areena H 2K
Posts: 69
Joined: Wed Dec 05, 2018 12:18 am

Re: Sig Fig Mistakes

Postby Areena H 2K » Sun Oct 06, 2019 12:58 am

The sig fig rules depend on if a certain amount of them are given in the problem, if they are then your final answer should contain the same amount of sig figs, if they are not then depending on multiplying/division you use the sig figs of the smallest number for your answer and for addition and subtraction, you use the one with the least decimal places in your answer.

Alan Cornejo 1a
Posts: 49
Joined: Fri Aug 30, 2019 12:15 am

Re: Sig Fig Mistakes

Postby Alan Cornejo 1a » Sun Oct 06, 2019 9:53 pm

Typically the amount of significant figures used for your answer is determined by the amount gaven to you in the question. Usually it follows these rules
any non-zero digits are always significant.
Any zeros between two significant digits are still significant.


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