Question

Average atomic weight of boron is 10.10 and boron
exists in two isotopic forms B10 and B11 The
percentage abundance of B10 is​

Answer 1

The percentage abundance of B-10 is 90%

What are isotopic forms?

• Isotopes are atoms of the same element, which have same atomic number but have different mass numbers.
• The atomic number is characteristic of the element, which is the number of protons.
• Mass number is the total number of protons and neutrons.
• So isotopes differ in number of neutrons.

In this question,

Given:

• Boron has 2 isotopic forms B-10 and B-11
• Average atomic weight = 10.10

To be Found:

% abundance of B-10 isotope

Let the % abundance of B-10 be x %,

So the % abundance of B-11 is (100 - x ) %

$Average\hspace{ 1 mm}atomic\hspace{ 1 mm}weight = \frac{10x + (100-x)*11}{100}$

We put the value of average atomic weight as given,

⇒ $10.10 = \frac{10x + (100-x)*11}{100}$

By cross multiplying,

⇒ $1010 = 10X + 1100 - 11x$

By simplifying and bringing similar terms together,

⇒$11x-10x= 1100 - 1010$

⇒$x= 90 \%$

So, the percentage abundance of B-10 is 90%