Use the data given in the following table to calculate the molar mass of naturally occuring argon isotopes:

$\begin{array}{ccc}\text{Isotopes}& \text{Isotopic molar mass}& \text{Abundance}\\ {}^{36}\text{Ar}& 35.96755gmo{l}^{-1}& 0.337\%\\ {}^{38}\text{Ar}& 37.96272gmo{l}^{-1}& 0.063\%\\ {}^{40}\text{Ar}& 39.9624gmo{l}^{-1}& 99.600\%\end{array}$

Description:

Molar mass of argon $=\Sigma m_i\frac{A_i}{100}$

$m_i=\text{isotopic molar mass}$

$A_i=\%\text{abundance of isotope}$

$\text{Molar mass of Argon}=(35.96755\times \frac{0.337}{100})+(37.96272\times \frac{0.063}{100})+(39.9624\times \frac{99.600}{100})$

$=[0.121+0.024+39.802]gmo{l}^{-1}=39.947gmo{l}^{-1}$

Final Answer:
The molar mass of naturally occuring argon isotope is $39.947gmo{l}^{-1}$.