The chloride of an unknown metal is believed to have the formula MCl3. A 2.395-g sample of the compound contains 3.606 * 10-2 mol Cl. Find the atomic mass of M.

Stoichiometry is the method of calculating the relative quantities of reactants and products in chemical reactions. In stoichiometry, the law of conservation of mass dictates that the mass of the reactants must equal the mass of the products. To perform stoichiometric calculations, one key step is to interpret the chemical formula, like MCl₃ in this exercise, which provides the ratio in which the elements combine.

For instance, in our exercise, the formula MCl₃ indicates that each molecule of the compound consists of one atom of the unknown metal M and three atoms of chlorine (Cl). When the problem states that there are 3.606 × 10^-2 mol Cl in the sample, we must realize that since chlorine is triply present in the chemical formula compared to the unknown metal, the moles of the metal will be exactly a third of the chlorine's moles. This concept is fundamental to moving on to finding the mass and eventually the atomic mass of the unknown metal.

The concept of molar mass is intrinsic to the calculations in this problem. The molar mass is the mass of 1 mole of a substance, usually expressed in grams per mole (g/mol). It is a bridging factor that connects the amount of substance (in moles) to its mass. When we talk about the 'atomic mass' of an element, we are often referring to its 'molar mass' on the periodic table.

In the solution steps, it is crucial to use the known molar mass of chlorine, which is approximately 35.45 g/mol, to calculate the total mass of chlorine in the sample. Through this, you can then determine the mass of the unknown metal and hence deduce its atomic mass. Calculating molar mass is a fundamental skill for understanding the quantitative aspects of a chemical formula and ensuring accuracy in stoichiometry.

A chemical formula provides important information about a compound, including the elements present and the ratio of atoms in the compound. Understanding the chemical formula is pivotal for any stoichiometry problem. While the formula reflects the qualitative composition, it also serves as a map for quantitative relationships during a calculation. A proper grasp of chemical formulas can help prevent errors in determining molar ratios.

For our example with the compound MCl₃, a 2.395-g sample holds the key to the metal's identity. The '3' in MCl₃ is particularly important as it dictates the essential 1:3 ratio of metal M atoms to Cl atoms. When this ratio is utilized correctly, as it is in dividing the moles of Cl by 3 to find the moles of metal M, it fills in the piece of the puzzle needed to unveil the atomic mass of metal M. Recognizing and applying this information correctly is a crucial part of achieving the correct solution.