Which sample contains the greatest number of atoms? (a) 27.2 g Cr (b) 55.1 g Ti (c) 205 g Pb

Understanding the molar mass of an element is the first step towards comparing quantities in chemistry. The molar mass is the mass of one mole of a substance, which is essentially the mass of 6.022 × 10^23 particles of the substance - thanks to Avogadro's number. Calculating molar mass is straightforward: you simply refer to the periodic table to find the atomic weight of each element.
For instance, the molar mass of Chromium (Cr) is approximately 52.00 grams per mole. This figure is pivotal when converting between grams and moles, as it sets the foundation for understanding the overall composition of a sample in terms of the number of particles it contains.
Knowing the molar mass assists in solving many stoichiometry problems, which involve the quantitative aspects of chemical reactions. By calculating this figure, students can easily transition to finding the number of moles and, consequently, the number of particles in a substance efficiently.

A cornerstone of the mole concept in chemistry is Avogadro's number, which is 6.022 × 10^23. This vast number indicates the quantity of particles, exactly atoms or molecules, in one mole of a substance. Avogadro's number bridges the gap between the microscopic world of atoms and the macroscopic world we experience every day.
When you're given the number of moles of a substance, you can multiply it by Avogadro's number to determine the number of atoms or molecules present. In our exercise example, knowing the number of moles of Chromium, Titanium, and Lead, and multiplying by Avogadro's number gives us the absolute count of atoms, facilitating easy comparison of different samples.

When presented with various samples of elements, being able to compare the number of atoms present in each sample is a practical application of the mole concept. Following the determination of the molar mass and consequent calculation of the number of moles in each sample, Avogadro's number empowers you to scale up from moles to the actual number of atoms.
This aspect of comparing atoms is crucial because it allows for a direct comparison of the elemental content irrespective of the differences in their atomic masses. Hence, whether you're working with a lightweight element like Lithium or a heavy one like Uranium, you can quantify and compare their atomic constitution comprehensively.

Stoichiometry is essentially the chemistry version of a recipe. It is the aspect of chemistry that concerns the calculation of the quantities of reactants and products in chemical reactions. The concept relies heavily on the mole as a counting unit, molar mass calculations, and Avogadro's number to ensure that chemical equations are balanced both in terms of mass and atom count.
In practice, stoichiometry enables chemists to predict how much of a reactant is needed to produce a desired amount of product. In our context, it helps in understanding the relationship between the masses of samples and the number of atoms. Stoichiometry is not only fundamental to laboratory applications but also forms the basis for calculating yields of reactions and scaling up from laboratory to industrial production.