Relative atomic mass
4 marks · NormalThe table shows the abundances of three isotopes of element X.
| Isotope | Relative Mass | % Abundance |
|---|---|---|
| X-10 | 10 | 20 |
| X-11 | 11 | 50 |
| X-12 | 12 | 30 |
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
11.1 (±0.1)
Also accept: 11.1; 11.10
Common mistakes: Not dividing by 100; Multiplying abundance instead of using as percentage
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Correctly multiplies each isotope's mass by its percentage abundance.
M2 · 1 mark · Sums the results of all isotopes.
M3 · 1 mark · Divides total by 100.
A1 · 1 mark · Final correct answer: 11.1 (to 1 decimal place). (follow-through)
Worked solution