The atomic weight of a newly discovered e ement is 98.225 amu. It has two naturally occuring isotopes. One isotope has a mass of 96.780 amu. The second isotope has a percent abundance of 41.7%. What is the mass of the second isotope?

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Answer 1 · 2018-05-09T08:43:11

$100.245 amu$ $100.245"amu"$

$M_{r} = \frac{\sum (M_{i} a)}{a}$ $M_r=(sum(M_ia))/a$ , where:

$98.225 = \frac{96.780 (100 - 41.7) + M_{i} (41.7)}{100}$ $98.225=(96.780(100-41.7)+M_i(41.7))/100$

$M_{i} = \frac{98.225 (100) - 96.780 (58.3)}{41.7} = 100.245 amu$ $M_i=(98.225(100)-96.780(58.3))/41.7=100.245"amu"$