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Using the information in the table, calculate the average atomic mass of strontium. Report to two decimal places.

[tex]\square \, \text{amu}[/tex]

\begin{tabular}{|r|r|r|}
\hline \multicolumn{3}{|c|}{ Strontium } \\
\hline Isotope & Mass (amu) & Abundance \\
\hline [tex]$Sr-84$[/tex] & 83.913428 & [tex]$0.56\%$[/tex] \\
\hline [tex]$Sr-86$[/tex] & 85.909273 & [tex]$9.86\%$[/tex] \\
\hline [tex]$Sr-87$[/tex] & 86.908902 & [tex]$7.00\%$[/tex] \\
\hline [tex]$Sr-88$[/tex] & 87.905625 & [tex]$82.58\%$[/tex] \\
\hline
\end{tabular}



Answer :

GinnyAnswer
To calculate the average atomic mass of strontium, we need to take into account both the masses and the abundances of its isotopes. Below is a step-by-step solution to find the average atomic mass:

1. Convert the Percent Abundances to Decimal Form:

- For \( \text{Sr-84} \):
[tex]\[ 0.56\% = 0.56 / 100 = 0.0056 \][/tex]

- For \( \text{Sr-86} \):
[tex]\[ 9.86\% = 9.86 / 100 = 0.0986 \][/tex]

- For \( \text{Sr-87} \):
[tex]\[ 7.00\% = 7.00 / 100 = 0.0700 \][/tex]

- For \( \text{Sr-88} \):
[tex]\[ 82.58\% = 82.58 / 100 = 0.8258 \][/tex]

2. Multiply the Mass of Each Isotope by Its Decimal Abundance:

- For \( \text{Sr-84} \):
[tex]\[ 83.913428 \times 0.0056 = 0.4704 \][/tex]

- For \( \text{Sr-86} \):
[tex]\[ 85.909273 \times 0.0986 = 8.4675 \][/tex]

- For \( \text{Sr-87} \):
[tex]\[ 86.908902 \times 0.0700 = 6.0836 \][/tex]

- For \( \text{Sr-88} \):
[tex]\[ 87.905625 \times 0.8258 = 72.5983 \][/tex]

3. Sum These Products to Find the Average Atomic Mass:

[tex]\[ \text{Average Atomic Mass} = 0.4704 + 8.4675 + 6.0836 + 72.5983 = 87.6198 \][/tex]

4. Round the Result to Two Decimal Places:

[tex]\[ \text{Average Atomic Mass} \approx 87.62 \, \text{amu} \][/tex]

So, the average atomic mass of strontium is:
[tex]\[ \boxed{87.62} \, \text{amu} \][/tex]

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