- Gallium consists of two isotopes of masses 68.95amu and 70.95amu with abundance of 60.16% and 39.84%, respectively. What is the average atomic mass of gallium? ( Ans: ca. 69.75)
- Naturally occurring cupper exists in two isotopic forms: 63Cu and 65Cu. The atomic mass of copper is 63.55amu. What is the approximate abundance of 63Cu? (Ans: ca. 70%)
- Naturally occurring element X exists in three isotopic forms: X-28 (27.977amu, 92.21% abundance), X-29(28.976amu, 4.70% abundance), and X-30 (29.974amu, 3.09% abundance). Calculate the atomic weight of X. (Ans: ca. 28.1amu)
- The atomic mass of rhenium is 186.2. Given that 37.1% of natural rhenium is rhenium 185, what is the other stable isotope? (Ans: 187Re )
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