Question

When a sample of element is vaporized and injected into a mass spectrophotometer, the results shown below are obtained. Use these results to estimate the average atomic mass of this element.

• A. $10.0amu$
• B. $10.2amu$
• C. $10.5amu$
• D. Cannot be determined; more information is required.

Answer 1

The correct option is B $10.2amu$

Average atomic mass $=f_1{M}_1+f_2{M}_2+\dots +f_n{M}_n$ where $f$ is the fraction representing the natural abundance of the isotope and $M$ is the mass number (weight) of the isotope.

The average atomic mass $=\frac{[10\times 80.1]+[11\times 19.9]}{80.1+19.9}=10.2$ amu.

Hence, option $B$ is correct.