Question

Element Q has three isotopes. The first has a mass of 25.3708 amu and makes up 30.89 % of a standard sample. The second isotope has a mass of 26.5979 amu and makes up 42 % of a standard sample. The third isotope has a mass of 27.8941 amu and makes up the remainder of a standard sample. What is the average atomic mass of this element?

Answer 1

This is a weighted average.

Just Sum up all the percentages * weight

ex if a room had 10 people in which

5 weighed 100kg

3 weighed 90kg

2 weighed 60kg

average weight would be = 100(5/10) + 90(3/10) + 60(2/10)

Answer 2

not that the fractions are the 'probability' of selecting a person at that weight