Question

question 15 please today is my test

Answer 1

Boron has two isotopes B10 here 10 is the atomic mass of the isotope the same is with B11 therefore we can apply the formula here,

Avg atomic mass = %abundance of 1st isotope x atomic mass + %abundance x atomic mass of 2nd isotope

Now as we dont know the % abundances we can take them as "X" and 100-X and the average atomic mass is given as 10.8 u we can take the round figure as 11!

Substitute all the values in the above mentioned formula like so;

11 = X * 10 + (100-X) * 11

11 = 10X + 110 - 11X

11 = 10X - 11X + 110

11 = -X + 110

X = 110 \ 11

X = 10

Substitute the X value in (100-X) which is = 90

Therefore the % abundance of B 10 is 10 % and the % abundance of B11 is 90%

HOPE THIS HELPED YA! :)