Question

The average atomic mass of a sample of an element X is 16.2 u. Predict the
percentage of isotopes x and "x in the sample.​

Answer 1

16.2 = 16 × x/100 + 18 × (100-x)/100. Thus the percentage of X in the sample is 90℅. The percentage of the other isotope X in the sample will be 100-90 = 10%.

Answer 2

Answer:

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 %

Hope It helps You!