Question

The average atomic mass of a sample of an element X is 16.2u. What are the percentages of isotopes 16 8X & 18 8X in the sample. Plzz answer fast

Answer 1

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Answer 2

Lets take the percentage of the  isotope of  16 8 X as  --> x %

So , the percentage of the  isotope of 18 8X ---> (100 - x) %

We are given the average atomic mass as 16.2

$\frac{x}{100}$ × 16 + $\frac{(100 - x)}{100}$ × 18 = 16.2

$\frac{16x}{100}$ +$\frac{1800 - 18 x}{100}$ = 16.2

$\frac{16x + 1800 - 18 x}{100} = 16.2$

$\frac{-2x + 1800}{100} = 16.2$

-2x + 1800 = 16.2 × 100

-2x + 1800 = 1620

-2x = 1620 - 1800

-2x = -180

x = $\frac{-180}{-2}$

x = 90 %

Therefore , percentage of isotope of  16 8 X = 90 %

percentage of isotope of  18 8 X = 100 - x = 100 - 90 = 10 %