Question

Boron has two common isotopes, B-10 (isotopic mass: 10.012937 amu) and B-11

isotopic mass: 11.009305 amu.) determine the percent abundance of B-11
a) 80%
b) 85%
c) 90%
d) 95%

Answer 1

The percent abundance of B-11 in boron is 80%, when considering its isotopic mass and the atomic mass calculation, which is consistent with the boron average mass. This answer is in line with option b) provided in the question.

Step-by-step explanation:

To determine the percent abundance of B-11, we can use the given isotopic masses and the provided information about boron isotopes. For boron (B), a sample consists of 20% B-10 with an isotopic mass of 10.012937 amu and 80% B-11 with an isotopic mass of 11.009305 amu. The average atomic mass of boron is calculated using the formula:

average atomic mass = (percent abundance of B-10 x mass of B-10) + (percent abundance of B-11 x mass of B-11)

Substituting the given values in the formula, we get:

average atomic mass = (0.20 x 10.012937 amu) + (0.80 x 11.009305 amu)

This simplifies to:

average atomic mass = (2.0025874 amu) + (8.807444 amu)

average atomic mass = 10.8100314 amu

Therefore, the percent abundance of B-11 is indeed 80%, corresponding to option b).

The atomic mass of boron calculated here, 10.8 amu, is consistent with the boron average mass presented in various scientific contexts.