Use the data given in the following table to calculate the molar mass of naturally occuring argon : \(\begin{array}{lcc}\text { Isotope } & \text { Isotopic molar mass } & \text { Abundance } \\ { }^{36} \mathrm{Ar} & 35.96755 \mathrm{~g} \mathrm{~mol}^{-1} & 0.337 \% \\ { }^{38} \mathrm{Ar} & 37.96272 \mathrm{~g} \mathrm{~mol}^{-1} & 0.063 \% \\ { }^{40} \mathrm{Ar} & 39.9624 \mathrm{~g} \mathrm{~mol}^{-1} & 99.600 \%\end{array}\)

Understanding the isotopic molar mass is crucial when studying chemistry, particularly when dealing with various isotopes of an element. An isotope is an atom that has the same number of protons as other atoms of the same element but differs in the number of neutrons. Consequently, isotopes of a given element exhibit different molar masses. The isotopic molar mass is the mass of one mole of a specific isotope of an element and is typically expressed in grams per mole (g/mol).

For instance, the isotopes of argon in the exercise are Ar-36, Ar-38, and Ar-40, with isotopic molar masses of 35.96755 g/mol, 37.96272 g/mol, and 39.9624 g/mol, respectively. These values indicate the mass of one mole of each respective isotope, helping to account for their individual contributions to the average molar mass of natural argon.

Percent abundance refers to the percentage of a particular isotope naturally found in a sample of elements. For a comprehensive understanding, it's essential to convert this percentage into a decimal form, as demonstrated in the original exercise solution. This conversion is executed by dividing the percentage by 100.

To illustrate, in the case of argon, Ar-36 has a percent abundance of 0.337%, Ar-38 has 0.063%, and Ar-40 has 99.600%. In decimal form, these percent abundances are 0.00337, 0.00063, and 0.99600, respectively. These decimal values are used to calculate the individual contributions of each isotope to the element's weighted average molar mass.

The weighted average molar mass is a reflection of the average mass of all isotopes of an element, considering their natural abundance. It is calculated by multiplying the isotopic molar mass of each isotope by its abundance (in decimal form), summing these products together to derive the overall molar mass of the element as it naturally occurs. This concept is particularly valuable because most elements exist as a blend of various isotopes.

To compute the weighted average molar mass of argon from the exercise, multiply the isotopic molar mass of each isotope (Ar-36, Ar-38, Ar-40) by its respective abundance in decimal form and add these amounts together. As a result, the weighted average accounts for the most abundant isotope heavily, while the less abundant isotopes have a smaller effect on the calculation.