Calculate the average atomic mass of b. the isotopes and abundances are 10b, 19.80% and 11b, 80.20%. round answer to 3 significant digits. a. 1.98 amu b. 10.8 amu c. 10 amu d. 8.82 amu

Given,

The two isotopes of B are 10B and 11B

% abundance of 10B = 19.80

% abundance of 11B = 80.20

Average atomic mass of B

=

=

=

=

= 10.802

Therefore, the average atomic mass of B is 10.802 u

Correct option is B.

Explanation: In this question, we are given two isotopes of Boron.

Mass of isotope

Mass of isotope

Fractional abundance can be calculated as:

Fractional abundance of isotope

Fractional abundance of isotope

To calculate average atomic mass of an element, we use:

Now, putting the values of abundances and mass number of 2 isotopes in above equation, we get:

Average Atomic Mass of B = 10.802 amu

Rounding it off to 3 significant figures, we get

Average atomic mass of B = 10.8 amu.

the answer is 303.15 or 303