Question

The Relative Atomic Mass Of Boron Having Isotopes B510 And B511 Is 10.8. What Is The % Of B511

Answer 1

GIVEN: isotopes of boron, $B_{10}$ and $B_{11}$

TO FIND: percentage of $B_{11}$

SOLUTION: here the two isotopes of boron are given whose atomic        masses are given as 10 and 11. the average atomic mass is 10.8.

We can assume that both the isotopes of boron contribute to 100% boron .

Lets say that the percentage of $B_{11}$ is x% and that of $B_{10}$ will be (100-x)%

Then,

Relative atomic mass =  (11 × x) + (10 × {100-x} / 100

10.8 = 11x + 1000- 10x / 100

10.8 = x + 1000 / 100

1080 = x + 1000

x = 1080 - 1000

x = 80%

and percentage of $B_{10}$ = 100-x

                                      = 100- 80

                                      = 20%

therefore the percentage of $B_{11}$ is 80%