Chapter 4.3, Problem 18PP

Interpretation Introduction

Interpretation:

Atomic mass of boron needs to be determined, if it has two naturally occurring isotopes.

Concept introduction:

Isotope is the same number of protons and electrons but have a different number of neutrons in an atom of the same element.

Answer to Problem 18PP

The atomic mass of Boron is $10.81amu$.

Explanation of Solution

Atomic mass is the mass of an atom that is expressed in atomic mass unit or amu. Its SI unit is kilogram, but sometimes it is expressed in non-SI unit, that is Dalton (Da or u).

Now

The mass contribution of isotope B-10:

$(mass)\times (percentabundance)=10.013amu\times 0.198amu=1.98amu$

Mass contribution of isotope B-11 is:

$(mass)\times (percentabundance)=11.009amu\times 0.802amu=8.83amu$

Thus, the atomic mass $=1.98amu+8.83amu=10.81amu$

Conclusion

Hence, the atomic mass of boron is $10.81amu$.