Question

Boron has two naturally-occurring isotopes. Boron-10 has an abundance of 19.8% and actual mass of 10.013 amu, and boron-11 has an abundance of 80.2% and actual mass of 11.009 amu. What is the average atomic mass for all isotopes of boron?

A 10.0 amu

B 10.5 amu

C 10.511 amu

D 10.812 amu

Answer 1

D) 10.812

Step-by-step explanation:

Given:

The two isotopes of boron (B).

Boron-10 has an abundance of 19.8% and Boron -11 has an abundance of 80.2%

To find:

The atomic mass of europium.

Solution:

Mass of Boron-10 = 10.013 amu

The percentage abundance of Boron-10 = 19.8%

The fractional abundance of Boron-10 =0.198

Mass of Boron-11 = 11.009 amu

The percentage abundance of Boron-11= 80.2%

The fractional abundance of Boron-11= 0.802

The average atomic mass of Boron = A.M

A.M = Mass of isotope x Fractional abundance of isotope

= 10.013amu x 0.198 +11.009amu x 0.802 = 10.81u

Therefore, D) 10.812 amu is the atomic mass of boron.