A sample of oxygen atoms contain only `._(8)O^(16)` and `._(8)O^(18)` isotopes. If the average atomic mass of the sample is 16.8, then identify the options which correctly tells the % composition of `._(8)O^(16)`?

Explanation

It is given that the average atomic mass of the sample of element X is 16.2 u.
Let the precentage of isotope 18/8 X y%. Thus, the perecent of isotope 16/8 Xwill be (100-y) %.
`18 x(y)/(100) + 16x((100-y))/(100) = 16.2`
`(18y)/(100) +(16(100-y))/(100) = 16.2`
`(18y + 1600 - 16 y)/(100)= 16.2`
18y + 1600-16y = 1620
2y + 1600= 1620
2y = 1620 - 1600
y= 10
Therefore, the isotope 18 /8X is 10%
And, the perecentage of isotope 16/ 8 is (100-10)% = 90%