The average atomic mass of lithium is 6.941 amu.Lithium has two naturally occurring isotopes, ⁶Li (7.52%) and ⁷Li (92.48%).The mass of ⁶Li is 6.0151 amu.What is the isotopic mass of ⁷Li?

Question

Quizplus · Accepted Answer

The isotopic mass of $ ^7Li $ can be calculated using the formula for average atomic mass: $$ \text{Average atomic mass} = \sum (\text{fractional abundance} \times \text{isotopic mass}) $$ Given that the average atomic mass of lithium is 6.941 amu, and we have the isotopic mass and abundance for $ ^6Li $ (6.0151 amu and 7.52%), we can solve for the isotopic mass of $ ^7Li $ as follows: $$ 6.941 = (0.0752 \times 6.0151) + (0.9248 \times \text{isotopic mass of } ^7Li) $$ Solving for the isotopic mass of $ ^7Li $ gives approximately 7.016 amu.

The Average Atomic Mass of Lithium Is 6