Answer
The abundance is 52.2% and the atomic mass is 152.92018 amu
Work Step by Step
The atomic mass of europium is 151.964 amu
% Eu-153 = 100 - %Eu-151 = 100 - 47.8 = 52.2
$\frac{47.8}{100}$ x 150.9198 + $\frac{52.2}{100}$ x $A_{Eu-153}$ = 151.964
$A_{Eu-153}$ $\approx$ 152.92018 amu
