## Chemistry (7th Edition)

(a) Gallium-69 has the greater abundance. (b) Gallium-69 has a percent abundance of $60.11\%$, and Gallium-71 has that value equal to $39.89\%$.
(a) Since the atomic weight is closer to the weight of the gallium-69 isotope, it has the greater abundance. (b) X: Percent abundance of gallium-69. Y: Percent abundance of gallium-71. $(68.9256)(X) + (70.9247)(Y) = (69.7231)$ And, X + Y must equal 1. $X + Y = 1$ $--\gt$ $X = 1 - Y$ $(68.9256)(1 - Y) + (70.9247)(Y) = (69.7231)$ $68.9256 - 68.9256Y + 70.9247Y = 69.7231$ $1.9991Y = 69.7231 - 68.9256$ $1.9991Y = 0.7975$ $Y = \frac{0.7975}{1.9991} = 0.3989$ ---- Therefore: $X = 1 - Y = 1 - 0.3989 = 0.6011$ Representing those numbers in percent values: $X = 60.11\%$ $Y = 39.89\%$