Write a net ionic equation for the reaction with ammonia by which (a) silver chloride dissolves. (b) aluminum ion forms a precipitate. (c) copper(II) forms a complex ion.

Understanding chemical reactions is fundamental for anyone studying chemistry. In the simplest terms, a chemical reaction involves the transformation of one or more substances, known as reactants, into new substances, called products.

During a reaction, the bonds between atoms in the reactants are broken and new bonds are formed to create the products. This can involve the transfer of electrons in ionic compounds, where atoms gain or lose electrons to form ions. Reactions can be categorized in many ways, for example, as synthesis, decomposition, single replacement, double replacement, combustion, or acid-base reactions.

When working with chemical reactions, it's important to write a balanced equation. This represents the conservation of mass, meaning the same number of each type of atom must exist on both sides of the equation. For instance, the reaction of silver chloride with ammonia features a single replacement and can be described by a balanced chemical equation. It shows us precisely what reactants are needed and what products are formed, and it allows us to predict the amounts of substances consumed and created.

Solubility and precipitation are two sides of the same coin when discussing the dissolving and crystallizing of substances. Solubility refers to the ability of a substance (the solute) to dissolve in a solvent, such as water, to form a homogeneous mixture or solution. Conversely, precipitation occurs when a solute exceeds its solubility in a solvent, causing it to form a solid, known as a precipitate.

Solubility is influenced by factors such as temperature, pressure, and the nature of the solute and solvent. As for precipitation reactions, they typically occur in aqueous solutions where two soluble salts react to form one insoluble salt that precipitates, alongside another soluble salt.

For example, when aluminum ions react with ammonia and water, aluminum hydroxide precipitates. It's crucial to determine which compounds will precipitate under certain conditions, a skill crucial not only for chemists but also for fields such as environmental science and medicine.

Complex ion formation is a chemical process where a central metal ion is surrounded by molecules or ions, commonly known as ligands. Ligands are species that can donate a pair of electrons to the metal ion, thus forming a coordinate covalent bond. The resulting charged entity is known as a complex ion.

The number of ligands that attach to a metal ion depends on the size, charge, and electron configuration of the metal ion as well as the size and electron-donating ability of the ligands. This gives rise to a variety of possible geometries for the complex ion, such as octahedral, tetrahedral, or square planar.

An example from our exercise is the formation of a copper(II) complex ion with ammonia. When ammonia ligands coordinate to a copper(II) ion, they donate lone pairs of electrons to the metal ion, creating a complex. This process is significant in biochemical systems and is extensively used in industrial applications, such as in the purification of metals or the colorimetric detection of substances.