A solid pink salt has the formula \(\mathrm{CoCl}_{3} \cdot 5 \mathrm{NH}_{3} \cdot \mathrm{H}_{2} \mathrm{O}\). When \(\mathrm{AgNO}_{3}\) is added to the pink solution containing \(0.0010 \mathrm{~mol}\) of the salt, \(0.43 \mathrm{~g}\) of \(\mathrm{AgCl}\) precipitates. Heating the salt produces a purple solid with the formula \(\mathrm{CoCl}_{3} \cdot 5 \mathrm{NH}_{3}\). (a) Write the correct formula and name of the pink salt. (b) When \(\mathrm{AgNO}_{3}\) is added to a solution containing \(0.0010 \mathrm{~mol}\) of the purple salt, \(0.29 \mathrm{~g} \mathrm{of} \mathrm{} \mathrm{AgCl}\) precipitates. Write the correct formula and name of the purple salt.

Understanding the calculation of molecular weight is fundamental in inorganic chemistry as it lays the groundwork for analytical techniques such as stoichiometry. It entails summing the atomic masses of all atoms in a molecule.

For example, the molecular weight of AgCl is computed by adding the atomic weight of silver (Ag), which is roughly 107.87 g/mol, to that of chlorine (Cl), approximately 35.45 g/mol. This results in AgCl having a molecular weight of 143.32 g/mol.

• The ability to calculate molecular weight is crucial, especially when determining the moles of a substance that has precipitated from a reaction, as seen in our textbook exercise.
• By dividing the mass of the substance by its molecular weight, we can find the number of moles — this step is often the starting point for many stoichiometric calculations.

Stoichiometry is the backbone of chemical equations, illustrating the quantitative relationships between reactants and products in a chemical reaction. It enables chemists to predict the amounts of substances consumed and produced in a given reaction.

In our exercise, stoichiometry is employed to deduce the ratio of Cl^- ions to the pink and purple salts based on the moles of AgCl precipitated. This tells us that the pink salt contains three Cl^- ions for every mole, while the purple salt has two Cl^-. Such stoichiometric calculations are pivotal in confirming chemical formulas and understanding chemical reactions.

• Mastering stoichiometry calls for a solid comprehension of mole concept, and the ability to balance chemical equations as well as convert between masses, moles, and molecules of different compounds.

Coordination compounds, such as the pink and purple salts in our exercise, possess a central metal atom or ion bonded to a set of molecules or ions called ligands. These compounds are unique and fascinating due to their colors, which arise from complex electronic interactions.

The naming of coordination compounds follows specific rules that consider the metal's oxidation state and the nature of the ligands. In our example, the pink salt, hexaamminecobalt(III) chloride monohydrate, denotes cobalt in a +3 oxidation state, with six ammine ligands and a chloride counter ion plus water of hydration.

• Understanding the chemistry of coordination compounds, including their nomenclature, is essential for in-depth knowledge of transition metal chemistry and applications in various fields like biochemistry and materials science.

Conceptual Clarity in Naming

Learning proper naming conventions in coordination chemistry can initially be challenging. However, it becomes intuitive with practice as it reflects the compound's precise chemical composition.