Question

The table below gives the data that is needed to calculate the average atomic mass of element B. Isotope Atomic mass (amu) Relative abundance (%) B-10 10.01 19.91 B-11 11.01 80.09 Based on these data, what is the average atomic mass of element B? 10.01 10.51 10.81 11.01

Answer 1

10.81u

Step-by-step explanation:

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Answer 2

`\boxed{\text{10.81 u}}`

Step-by-step explanation:

The atomic mass of B is the weighted average of the atomic masses of its isotopes.

We multiply the atomic mass of each isotope by a number representing its relative importance (i.e., its percent of the total).

Set up a table for easy calculation:

`\begin{array}{ccccr}\textbf{Atom} & \textbf{Mass/u} &\textbf{Percent} & \textbf{Calculation}& \textbf{Result}\\^(10)\text{B}& 10.01 & 19.91 & 10.01 * 0.1991 & 1.99\\^(11)\text{B}& 11.01 & 80.09 & 11.01 * 0.8009 & 8.82 \\& & & \text{TOTAL} = &\textbf{10.81}\\\end{array}`

The average atomic mass of B is
`\boxed{\textbf{10.81 u}}`.