Question

multiple choice 10 points
an unknown compound is found to have the following stable isotopes:

isotope	atomic mass (amu)	percent abundance (%)
2	15.909	9.86
3	16.909	7.00
4	17.500	82.58

determine the weighted average atomic mass for this compound.
16.91
17.28
16.06
17.55

Explanation:

Step1: Convert percentages to decimals

$0.56\% = 0.0056$, $9.86\%=0.0986$, $7.00\% = 0.07$, $82.58\%=0.8258$

Step2: Calculate weighted - value for each isotope

For isotope 1: $13.913\times0.0056 = 0.0779128$
For isotope 2: $15.909\times0.0986=1.5686274$
For isotope 3: $16.909\times0.07 = 1.18363$
For isotope 4: $17.500\times0.8258 = 14.4515$

Step3: Sum up the weighted - values

$0.0779128+1.5686274 + 1.18363+14.4515=17.2816702\approx17.28$

Answer:

17.28