Average Atomic Mass Problems

1. What is average atomic mass of Lithium if 7.42% exists as ⁶Li (6.015 g/mol) and 92.58% exists as ⁷Li (7.016 g/mol)?

2. Magnesium has three naturally occuring isotopes. 78.70% of Magnesium atoms exist as Magnesium-24 (23.9850 g/mol), 10.03% exist as Magnesium-25 (24.9858 g/mol) and 11.17% exist as Magnesium-26 (25.9826 g/mol). What is the average atomic mass of Magnesium?

3. Neon has two major isotopes, Neon-20 and Neon-22. Out of every 250 neon atoms, 225 will be Neon-20 (19.992 g/mol), and 25 will be Neon-22 (21.991 g/mol). What is the average atomic mass of Neon?

4. What is the atomic mass of Hafnium if out of every 200 atoms, 10 have mass 176.00 g/mol, 38 have mass 177.00 g/mol, 54 have mass 178.00 g/mol, 28 have mass 179.00 g/mol, and 70 have mass 180.00 g/mol?

5. In a sample of 200 Chlorine atoms, it is found that 151 are ³⁵Cl (34.969 g/mol), and 49 are ³⁷Cl (36.966 g/mol). What is the average atomic mass of Chlorine?

6. Without doing any math, are there more Bromine-79 atoms or more Bromine-80 atoms on earth? (Hint: look at the periodic table.)