## If bromine atom is available in the form of, say, two isotopes 79 35Br (49.7%) and 81 35Br (50.3%), calculate the average atomic mass of bromine atom.

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Answer
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We know the percentage of
is
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49.7%
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And the percentage of
is
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50.3%
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We know that,

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Average mass of an isotope = (% existence of the isotope 1 x mass of isotope 1) +
**

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(% existence of the isotope 2 x mass of isotope 2)
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=
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(M1 x P1) + (M2 x P2)
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= (79 x 49.7 /100) + (81 x 50.3/100)
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= (79 x 497/1000) + (81 x 503 /1000)

= (39263/ 1000) + (40743/1000)

= 39.263 + 40.743

=
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80.006u
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Thus, the
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average atomic mass of bromine is 80u.
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