Uncertainty about relative atomic mass

In summary, relative atomic mass is the average mass of an element's atoms relative to the mass of an atom of carbon-12. It is calculated by taking the weighted average of the masses of all the naturally occurring isotopes of an element. There is uncertainty about relative atomic mass due to variations in isotope masses and the source of the element. This uncertainty is expressed as a range of values. Relative atomic mass is important in chemistry for accurately measuring substances and determining molar mass.
  • #1
Neutroniclad
14
0
For the uncertainty about relative atomic mass.
Such as for H-1 there is 1.00794(7)u.
what exactly does the "7"means?
Is it 1.007947? or 1.00794(+/-)0.000007? or something else?
ref: http://www.ciaaw.org/pubs/TSAW-2007.pdf
 
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  • #2
Neutroniclad said:
Is it 1.007947? or 1.00794(+/-)0.000007?
Neither. It is the uncertainty in the last digit, so 1.00794 ± 0.00007. (You had a zero too many.)
 
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FAQ: Uncertainty about relative atomic mass

1. What is relative atomic mass?

Relative atomic mass is the average mass of an element's atoms relative to the mass of an atom of carbon-12, which is assigned a mass of exactly 12 atomic mass units.

2. How is relative atomic mass calculated?

Relative atomic mass is calculated by taking the weighted average of the masses of all the naturally occurring isotopes of an element, taking into account their abundance.

3. Why is there uncertainty about relative atomic mass?

There is uncertainty about relative atomic mass because the masses of isotopes can vary slightly due to natural abundance and experimental limitations. Additionally, the relative atomic mass of an element can change depending on the source of the element.

4. How is uncertainty about relative atomic mass expressed?

Uncertainty about relative atomic mass is expressed as a range of values, typically with one or two decimal places. This range is based on the variations in the masses of the isotopes and the precision of the measurement.

5. Why is relative atomic mass important in chemistry?

Relative atomic mass is important in chemistry because it is used to accurately calculate and measure the amount of a substance in a chemical reaction. It is also used to determine the molar mass of a compound, which is essential in many chemical calculations.

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