Average Atomic Mass and Percent Abundance
Using your knowledge of atomic mass, calculate the average atomic masses of the elements in the following problems. Make sure to show all of your work and write your answers in the correct number of significant figures.
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Unknown Element: 92% of the atoms of an element have a mass of 28.0 atomic mass units, five percent have a mass of 29.0 atomic mass units and the remaining atoms have a mass of 30.0 atomic mass units. Calculate the average atomic mass and identify the element.
- Carbon: 98.9% of the atoms of carbon-12 have a mass of 12.0 amu. 1.10% of the atoms of carbon-13 have a mass of 13.0 amu. Calculate the average atomic mass of the isotopes of carbon.
- Nitrogen: 99.63% of the atoms of nitrogen-14 have a mass of 14.0 amu. 0.37% of the atoms of carbon-15 have a mass of 15.0 amu. Calculate the average atomic mass of the isotopes of nitrogen.
- Chlorine: 75.77% of the atoms of chlorine-35 have a mass of 35.0. 24.23% of the atoms chlorine-37 has a mass of 37.0 amu. Calculate the average atomic mass of the isotopes of chlorine.
- Silicon: 92.23% of the atoms of silicon-28 have a mass of 28.0 amu. 4.67% of the atoms silicon-29 has a mass of 29.0 amu. 3.10 % of silicon-30 has a mass of 30 amu. Calculate the average atomic mass of the isotopes of chlorine.
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