Chemistry
Grade-9
Easy
Question
The atomic mass of two isotopes are 85 and 87, with relative abundance of 75% and 25 % respectively. What is the average atomic mass?
- 50
- 80
- 85.5
- 60
Hint:
The average atomic mass of an element is defined as the weighted average of the masses of its naturally occurring isotopes.
The correct answer is: 85.5
The atomic mass of two isotopes are 85 and 87, with relative abundance of 75% and 25 % respectively.
The average atomic mass of an element is defined as the weighted average of the masses of its naturally occurring isotopes.
The average atomic mass = (0.75
85 + 0.2587) = (63.75 + 21.75) = 85.5
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