Question

Average atomic mass of a sample of an element X is 16.2u. What are the percentages of isotopes X- mass no.- 16 , atomic no. - 8
X- mass no. - 18 , atomic no. - 18

Answer 1

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

 × 16 +  × 18 = 16.2

+ = 16.2

-2x + 1800 = 16.2 × 100

-2x + 1800 = 1620

-2x = 1620 - 1800

-2x = -180

x = 

x = 90 %

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

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