What is the average atomic mass of bromine if it has 49.7% 79 35 Br and 50.3% 81 35 Br?

Given, 49.7% of 79 35 Br and 50.3% of 81 35 Br These isotopes are in the ratio = = Average atomic mass = ∴ Average atomic mass of bromine = 80 amu

Chemistry

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Given,

49.7% of ⁷⁹₃₅Br and

50.3% of ⁸¹₃₅Br

These isotopes are in the ratio = $\dfrac{49.7}{50.3}$ = $\dfrac{497}{503}$

Average atomic mass = $\dfrac{(79 \times 497)+(81 \times 503)}{1000}$

$= \dfrac{39263+(40743)}{1000} \\[1em] = \dfrac{80006}{1000} \\[1em] = 80.006 \text{ amu} \\[1em] \approx 80 \text{ amu}$

∴ Average atomic mass of bromine = 80 amu

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