The mass of the other isotope is 68.9254620 amu.
Let the first isotope (⁷¹Ga) be A
Let the other isotope be B
Let the mass of the other isotope be y
From the question given above, the following data were obtained:
Mass of A = 70.9247050 amu
Abundance (A%) = 39.892%
Abundance (B%) = 100 – 39.892
Abundance (B%) = 60.108%
Atomic mass of gallium = 69.723
The mass of the other isotope can be obtained as illustrated below:
69.723 = [(70.9247050 × 39.892)/100] + [(y × 60.108)/100]
69.723 = 28.2932833 + 0.60108y
Collect like terms
69.723 – 28.2932833 = 0.60108y
41.4297167 = 0.60108y
Divide both side by 0.60108
y = 41.4297167 / 0.60108
Therefore, the mass of the other isotope is 68.9254620 amu
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