Answer:
39.95 u
Explanation:
The formula for the calculation of the average atomic mass is:
[tex]Average\ atomic\ mass=(\frac {\%\ of\ the\ first\ isotope}{100}\times {Mass\ of\ the\ first\ isotope})+(\frac {\%\ of\ the\ second\ isotope}{100}\times {Mass\ of\ the\ second\ isotope})+(\frac {\%\ of\ the\ third\ isotope}{100}\times {Mass\ of\ the\ third\ isotope})[/tex]
Given that:
For first isotope, Argon-36:
% = 0.337 %
Mass = 35.97 u
For second isotope, Argon-38:
% = 0.063 %
Mass = 37.96 u
For third isotope, Argon-40:
% = 99.600 %
Mass = 39.96 u
Thus,
[tex]Average\ atomic\ mass=\frac{0.337}{100}\times {35.97}+\frac{0.063}{100}\times {37.96}+\frac{99.600}{100}\times {39.96}=0.1212189+0.0239148+39.80016=39.9452937[/tex]
Average atomic mass = 39.95 u
