Potassium chromate is isomorphous to potassium sulphate \(\left(\mathrm{K}_{2} \mathrm{SO}_{4}\right)\) and it is found to have \(26.78 \%\) Cr. Calculate the at.wt. of \(\mathrm{Cr}\) if at.wt. of potassium is \(39.10\).

The atomic weight, or atomic mass, of an element is a crucial concept in chemistry, detailing the average mass of atoms of an element, measured in atomic mass units (u). The atomic weight of an element can be derived from its isotopic composition and the relative atomic masses of its isotopes. In exercises involving isomorphous substances, like potassium chromate and potassium sulfate, understanding this concept is essential.

When given the percentage of an element in a compound and knowing that the compound is isomorphous with another with a known molecular formula, one can deduce the atomic weight of the element in question. The calculation involves determining the molar mass of the isomorphous compound and using the percentage to isolate the contribution of the given element to this molar mass, ultimately revealing the atomic weight of the element.

Percentage composition is pivotal in understanding the makeup of a compound. It reflects the percent by mass of each element present in the compound. The calculation demands the molar mass of the entire compound and the molar mass of the individual elements within it. You can determine the percentage composition of an element by dividing the total mass of the element in one mole of the compound by the molar mass of the compound, then multiplying by 100%.

In practice, this provides vital information regarding the proportion of elements, which can be used to derive empirical and molecular formulas of the compound. Additionally, for isomorphous substances, the percentage composition can be applied to infer the atomic weight of elements when one isomorph has unknown parameters and the other is already characterized.

The molar mass of a compound is the mass of one mole of its molecules, reported in grams per mole (g/mol). It's calculated by summing the atomic weights of each atom contained within the molecule, multiplying each by the number of times the atom appears in the formula. Knowledge of the molar mass is indispensable when converting between the mass of a substance and the number of moles or number of particles.For example, in the problem involving potassium chromate, the molar mass quantifies the grams of potassium chromate equivalent to one mole. This calculation is crucial to deduce the atomic weight of a constituent element, such as chromium, from its percentage composition in the isomorphous compound. Understanding molar mass calculations translates directly to substantial insights into the stoichiometry of reactions and the quantification of chemical compounds involved.