Wednesday, 13 February 2013

1.12 calculate the relative atomic mass of an element from the relative abundances of its isotopes

Relative atomic mass is the average weight of an atom of an element. There is variation in the weight due to the fact that there are different isotopes with in an element. (Different isotopes have different weights due to less or more neutrons.)

It is calculated like this:
(% of isotope x its mass) + (% of isotope x its mass) / 100

e.g for chlorine
75% of all chlorine has a mass of 35. 25% of all chlorine has a mass of 37.
(75 × 35) + (25 × 37)100
2625 + 925100
= 35.5

14 comments:

  1. (Different isotopes have different weights due to less or more protons.)
    its not protons, its neutrons :P

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  2. Shouldn't it be 75% and 25%?

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  3. 75% of all chlorine has a mass of 25% of all chlorine has a mass of 37. (makes no sense needs to be...)
    75% of all chlorine has a mass of 35. 25% of all chlorine has a mass of 37.

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  4. Sorry this post has been laced with mistakes, not sure what was going on when I wrote it ;P Thank you all for the help!

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  8. How do you find out the percentage of isotopes? Or is it always been given in the questions?

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