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13 votes
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Decimal places vs significant figures

My verdict on $0.064$ is three decimal places, two significant figures. The underlying philosophy is: how many figures would you give if you converted this to "scientific" notation - which would be $6....
TAR86's user avatar
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10 votes
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What do final zeros to the right of decimal point indicate?

"$2.000$" does not mean $2.000 \pm 0.0005$. "$2.000$" does not mean the interval [1.9995,2.0005]. "2.000" means that there is an unspecified amount of uncertainty in at ...
DavePhD's user avatar
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9 votes

What's the purpose of significant figures in measurements?

While estimating uncertainty can be quite involved, the purpose of significant figures is quite simple: They are a shorthand method of communicating the uncertainty of a measurement from those who ...
theorist's user avatar
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8 votes

Decimal places vs significant figures

There's no room for my two-pence on the matter. "Significant figures" and "decimal places" mean exactly what you think they do, and the online assignment is wrong. Pick out a random sampling of ...
gone's user avatar
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6 votes

What's the purpose of significant figures in measurements?

You are absolutely correct in that there are several kind of uncertainties (often called errors). These are referred to as systematic and statistical errors and the difference between them can be ...
Paul's user avatar
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6 votes

What's the purpose of significant figures in measurements?

Once upon a time, calculations were done on paper and on slide rules. It would take considerable effort to carry 10 digits in a calculation instead of 3 (which is what most slide rules are capable of)....
Karsten's user avatar
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6 votes
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Should durations of time be considered to determine final significant figures of answer?

[OP] When calculating sig-figs, do you consider the number of significant-figures for all given values, including durations, or just physical quantities? You consider all physical quantities ...
Karsten's user avatar
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5 votes
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Use of significant figures in addition and subtraction

No. The answer isn't accurate enough. Say, for example I wish to add two numbers: $1.23$ and $2.367$. I proceed like this, but I've no idea what the third digit after the decimal in $1.23$ is and so ...
Berry Holmes's user avatar
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5 votes
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Does the multiplication and division significant figures rule apply to unit conversions as well?

In regards to the calcium situation, it depends on whether you measured 40g of calcium (which would be 2 sig. fig.), or 40g was the stated value (1 sig. fig.). Yes, the number of sig figs in your ...
George Tian's user avatar
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5 votes
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How many significant digits are appropriate when one or more digits are eliminated (during subtraction)?

There's an easy way to look at this. Lets say the value $50.0$ refers to $\pu{50.0 cm}$ measured accurately to $\pu{0.1 cm}$, and that $49.6$ refers to $\pu{49.6 cm}$ measured accurately to $\pu{0.1 ...
Pritt says Reinstate Monica's user avatar
5 votes

Is precision measured by significant digits in chemistry?

The single measured values provided by 3 different tools gives us just a hint about possible accuracy or precision of the tools. The tool providing the value 1.39 is probably, but not necessarily ...
Poutnik's user avatar
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4 votes

Significant Figures

Significant figures are a sloppy method for doing error propagation. The point with significant figures is to maintain "reasonable" precision in the answer. Ideally you'd assume that the ...
MaxW's user avatar
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4 votes

Why do significant figure rules contradict each other?

Bear in mind the significant digit rules are just simplifications of the rules of absolute (+, -) and relative (*,/) variance propagation. The rule of significant digit numbers for summing is for 2 ...
Poutnik's user avatar
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4 votes

Significant figures and accuracy

Both method 1 and method 2 are wrong. The concept of useless significant figures should be wiped out from school curricula and replaced with proper statistics. This significant figures and concept of ...
AChem's user avatar
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4 votes

Number of significant figures to use in reporting the concentration of the titrand in acid-base titration

You said that you have done seven titrations, i.e., you have the set of concentrations $\{c_1, c_2, \ldots, c_7\}$. I offer you the following standard statistical approach to inform your concentration ...
Metal Storm's user avatar
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3 votes

Am I Using the Correct Number of Significant Figures (Heat Problem)?

This is sort of tricky, but I'd say that neither 10.8 nor 11 is right! You got $$Q_1 = 9.7\bar22753346\ \mathrm{kcal}$$ which you rounded to $9.72\ \mathrm{ kcal}$. The bar over the first two ...
MaxW's user avatar
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3 votes

Chemistry 101 - significant figures

Truthfully this seems like a poor question. Either (A) or (B) could be argued. (A) The ruler is marked in cm, so the measurement can only be made guaranteed to the cm. You can try to interpolate to ...
MaxW's user avatar
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3 votes

Significant Figures

As an error is not explicitly given and as your first number is $7.195$ g this means that the absolute error bound implied is 0.0005, which is to say that the error (uncertainty) is in the decimal ...
porphyrin's user avatar
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3 votes
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Uncertainty of Atomic Mass

First of all it is important to realize that the number you quote is not the atomic mass of magnesium, but the avarage (molar) mass of all naturally occuring isotopes. If you visit the wikipedia page ...
Paul's user avatar
  • 2,396
3 votes

What do final zeros to the right of decimal point indicate?

The zeros to the right of the decimal point denotes the expected precision of a measurement. Thus a value of 2.0 indicates that the the measurement falls in the interval [1.95,2.05[. The value 2.00 ...
Jeppe Nielsen's user avatar
3 votes

Percent error and significant figures?

Actually the % error is calculated as: $\frac{\text{experimental} - \text{actual}}{\text{actual}}\cdot100\%$ That way if experimental < actual then the error is negative if experimental > ...
MaxW's user avatar
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3 votes
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Significant figures of the product

According to Columbia University Website, Rules for Significant Figures are as follows: All non-zero numbers ARE significant: The number 33.2 has three significant figures because all of the digits ...
Mathew Mahindaratne's user avatar
3 votes

What is a reliable way of writing significant figures in multi-step problems?

For the following, I take 3 to have one significant figure, 67 to have 2 significant figures, and 100 to have one significant figure. If you want to avoid confusion with exact integers (such as a ...
Karsten's user avatar
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2 votes

How to solve a math expression with proper significant digits?

For the record, no scientist actually uses significant figures. They use error bars because you can quantify how big the uncertainty is beyond it is in such and such decimal place. There should be ...
Zhe's user avatar
  • 17.5k
2 votes

Ka relating to Dissociation of Weak acid and Water

I think MaxW's answer covers the gist of the question from the calculation side, but its also worth noting something else about your question. $\ce{H^+}$ and $\ce{H3O^+}$ are often used ...
Tyberius's user avatar
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2 votes
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Ka relating to Dissociation of Weak acid and Water

Yes, water autodissociates according to the equation $\ce{2H2O <=> H3O+ + OH-}$. But I should point out that the equilibrium constant is written as though the concentration of water itself is ...
MaxW's user avatar
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2 votes

Significant Figures Calculations

Your answer of $2500$ and the book's answer of $2523$ both have four significant figures. If you want to keep your answer to the same degree of accuracy as the given data with the least number of ...
Tazwar's user avatar
  • 131
2 votes

How do significant figures work on this computation?

Assuming the precision of the given volume, $V_1 = \pu{400 mL}$, is only to 1 significant figure (i.e. only the hundreds place digit of "4" is precise), then your final answer would be rounded to $V_2 ...
Len_sprague's user avatar
2 votes

A sample must not contain more than 2% contaminants to be pure. Are there instances where 2.12% is ok?

It depends mainly on the accuracy of your measuring instrument in practice and the accuracy required by your work. For example: If you want to make a solution with 2g solute in it, and to measure ...
knoftrix's user avatar
  • 355
2 votes

A sample must not contain more than 2% contaminants to be pure. Are there instances where 2.12% is ok?

It depends.... The statement "A sample must not contain more than 2% contaminants to be pure" is ambiguous as you have pointed out. To understand exactly what that means requires further ...
MaxW's user avatar
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