<p>Average Atomic Mass</p><p>. can be calculated given data from a mass spectrophotometer.</p><p>. % or relative abundance and isotope masss are needed to find a weighted average</p><p>. The final result will have units of amu (atomic mass units).</p><p>Sample calculations</p><p>1. A sample of neon gas was injected into a spectrophotometer and the print out included three peaks at 20,21,and 22 amu. The relative areas of the peaks were: 0.9092, 0.00257, and 0.0882 repectively. Calculate the atomic mass of neon</p><p>2. Chlorine has two stable isotopes. The mass of one is 34.97 amu and its relative abundance is 75.53% What is the mass of the other stable isotope?</p><p>3. The element indium exists as 2 isotopes. 113 In has a mass of 112.9043 amu and 115In has a mass of 114.9041 amu. The average atomic mass of indium is 11In has a mass of 114.9041 amu. The average atomic mass of indium is 114.82 Calculate the relative abundance of the two isotopes of indium. Complete the following:</p><p>4. The element magnesium has three stable isotopes with the following masses and abundances:</p><p>Isotope Mass (amu) Abundance Magnesium-25 23.9850 78.99% Magnesium-25 24.9858 10.00% Magnesium-26 25.9826 11.01%</p><p>Calculate the average atomic mass of magnesium.</p><p>5. An unknown sample of mystery element “T” is injected into a mass spectrophotometer. 7.42% of the element is present as 6T and 92.58% as 7T. the mass value for 6T is 6.02 amu 7.02 amu for 7T. What is the average atomic mass and what is the identity of the element?</p><p>6. Silicon has three stable Isotopes. Fill in the missing information. Hint: find Si average atomic mass on the periodic table.</p><p>Isotope Mass (amu) %abundance Silicon-28 27.89 ? Silicon-29 ? 4.70% Silicon-30 29.97 3.09%</p><p>7. Gallium has two stable isotopes of masses 68.38 (69Ga ) and 70.92 amu (71Ga). What are the relative abundances of the two isotopes?</p>