Question

If the average atomic mass of an element having two isotopes is 71, the ratio of the natural abundance of two isotopes of mass 70 and 74 will be ​

Answer 1

$$\begin{gathered} Averageatomicmass=\frac{x_1{M}_1+x_2{M}_2}{x_1+x_2} \\ {x}_1+x_2=100 \\ {x}_1=100-x_2 \\ Averageatomicmass=\frac{x_1{M}_1+x_2{M}_2}{x_1+x_2} \\ 71=\frac{(100-x_2)\times 70+x_2\times 74}{100} \\ 7100=7000-70x_2+74x_{2 \\ } \\ 100=4x_2 \\ {x}_2=\frac{100}{4}=25\% \\ {x}_1=75\% \end{gathered}$$