Question

The atomic mass of an element X is 16.24. What are the percentage of isotopes of 'X' having atomic number 8 and mass number 16 and 18.

Answer 1

Let the % of isotope ₈¹⁶X = x
Let the % of isotope ₈¹⁸X = 100 - x
Average atomic mass of an element X = 16.24
Now,
Average atomic mass=[(Mass of ₈¹⁶X )(% of ₈¹⁶X)+(Mass of ₈¹⁸X)(% of ₈¹⁸X)]/100
16.24 = (x) (16)+(100-x) (18)] / 100
16.24 = (16x + 1800 - 18x) / 100
1624 = 1800 - 2x
2x = 1800 - 1624
2x = 176
x = 176/2
x = 88
Hence, % of isotope ₈¹⁶X = 88%
and % of isotope ₈¹⁸X = 100 - 88 = 12%
This is the required answer.
Thanks.