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### Significant Figures

Posted: Sat Sep 29, 2018 1:18 pm
When using significant figures, do you use significant figures throughout your whole calculation (for example if the given significant figures is 2, but I am using molar mass and the molar mass contains 4 significant figures then do I change the molar mass to 2 significant figures or leave as is) or do you only apply significant figures for your answer?

### Re: Significant Figures

Posted: Sat Sep 29, 2018 1:30 pm
You can use however many significant figures you want for the molar mass and whatever other numbers are needed in the calculation, but eventually, your final answer has to have the same number of significant figures as the numbers provided in the problem.

### Re: Significant Figures

Posted: Sun Sep 30, 2018 6:25 pm
Significant figures only need to be applied in the final answer. In your example with the number of given sig figs as 2, but the molar mass having 4 sig figs, I recommend keeping the 4 molar mass sig figs throughout the calculation, and then giving your answer with 2 sig figs. Keeping all sig figs throughout the calculation, then applying the sig fig rules to the answer, will give the most accurate answer.

### Re: Significant Figures

Posted: Sun Sep 30, 2018 9:46 pm
Generally, you want to use exact values through the entire calculation until you reach your final answer. When you get to the final answer, you notate it according to the number with the least number of significant digits in the entire problem.

Hypothetical Example: 2.37 x 2.5 = 5.925

Lowest number of sig figs in problem = 2 (2.5)

Shorten answer to 5.9

### Re: Significant Figures

Posted: Mon Oct 01, 2018 11:36 am
You get the most accurate answer if you use the true value while you are calculating. Apply significant figures only to your final answer so you don't have rounding error.

### Re: Significant Figures

Posted: Mon Oct 01, 2018 11:47 am
To avoid rounding errors at the end, try not to round numbers within the calculation, only at the end. A useful way to do this, especially when calculations contain lots of significant figures, is to store step-by-step calculations in your calculator and recall them in order to keep the true value. This is really helpful for really large numbers, too.

### Re: Significant Figures

Posted: Mon Oct 01, 2018 11:49 am
I tend to use exact calculations throughout the problems ensuring there are no rounding errors by the end. Once I get my answer, then I take significant figures into consideration. I find this provides the most accurate answer.

### Re: Significant Figures

Posted: Mon Oct 01, 2018 4:46 pm
904928548 wrote:When using significant figures, do you use significant figures throughout your whole calculation (for example if the given significant figures is 2, but I am using molar mass and the molar mass contains 4 significant figures then do I change the molar mass to 2 significant figures or leave as is) or do you only apply significant figures for your answer?

From what I've read, you use the molar mass as stated on the periodic table; however, when multiplying the number with 2 significant figures and the molar mass which contains 4 significant figures your answer would only contain 2 significant figures because the rule for multiplying and dividing with significant figures states that the least number of significant figures in a problem determines the number of significant figures in the answer.

### Re: Significant Figures

Posted: Mon Oct 01, 2018 5:25 pm
Significant figures only come into play when the final answer is being evaluated. Therefore, a more accurate answer would be calculated if you used the exact molar mass and then rounded your final answer to the appropriate number of significant figures, in this case two.

### Re: Significant Figures

Posted: Mon Oct 01, 2018 6:28 pm
The full value of molar mass can be used to calculate whatever needs to be calculated, but the least amount of sig figs must be used when determining the final answer, as it would be inaccurate to have an answer that is more than the initial significant figures there given.

### Re: Significant Figures

Posted: Wed Oct 03, 2018 10:45 pm
When adding and subtracting, you use the least number of sig figs AFTER the decimal place.
For example, 1.823+9.75=11.57

9.57 has only 2 sig figs after the decimal place which means the answer will only have 2 sig figs after the decimal.