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Given relative abundance of the following naturally occuring isotopes of oxygen,...

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r4rob92 | (Level 1) Valedictorian

Posted September 24, 2012 at 9:54 AM via web

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Given relative abundance of the following naturally occuring isotopes of oxygen, calculate the average atomic mass: O-16: 99.76% , O-17: 0.037% , O-18: 0.204%

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted September 24, 2012 at 10:17 AM (Answer #1)

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The atomic mass of oxygen is the average mass of oxygen weighted with the abundance. For the isotope with mass 16, the concentration is 99.76% which is the weight to be used. For the isotope with mass 17, the concentration is 0.037% which is the weight. For the isotope with mass 18, the concentration is 0.204% which is the weight to be used.

The weighted average mass is: 16*0.9976 + 17*0.00037 + 18*0.00204 = 16.00461

The average atomic mass of oxygen is 16.00461

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