Question
Use the data given in the following table to calculate the molar mass of naturally occurring argon isotopes:
Isotope Isotopic molar mass Abundance
36Ar 35·96755 g mol–1 0·337%
38Ar 37·96272 g mol–1 0·063%
40Ar 39·9624 g mol–1 99.600%
Solution
Molar mass of Ar = 35.96755 x 0.00337 + 37.96272 x 0.0063 + 39.9624 x 0.99600
[0.121 +0.024+39.802] = 39.948 g mol-1
