Mercury ions (Hg2 2+) can be removed from solution by precipitation with Cl-. Suppose that a solution contains aqueous Hg2(NO3)2. Write complete ionic and net ionic equations to show the reaction of aqueous Hg2(NO3)2 with aqueous sodium chloride to form solid Hg2Cl2 and aqueous sodium nitrate.

Precipitation reactions are a cornerstone of analytical chemistry, often used for removing impurities or collecting products in a solid form from a liquid solution. They occur when two aqueous solutions combine to form an insoluble solid, known as the precipitate.

During the reaction, the ions from the differing compounds exchange partners, and when certain combinations of these ions are not soluble in water, a solid forms and falls out of the solution. The solubility of the ions in water is key to predicting whether a precipitation reaction will occur. To better understand these reactions, one can refer to the solubility rules—a guide used to predict which ionic compounds are soluble and which are not.

For example, when aqueous mercury(II) nitrate reacts with aqueous sodium chloride, a white solid mercury(I) chloride, or calomel, precipitates out of the solution, while sodium nitrate remains dissolved. This reaction confirms the presence of mercury ions in the solution and can also be used for its purification.

In the realm of chemistry, ionic equations provide a more detailed representation of reactions involving ionic compounds in solution. They are particularly useful for illustrating reactions in aqueous solutions where the compounds exist as ions rather than molecules.

An ionic equation is usually broken down into two parts: the complete ionic equation and the net ionic equation. The complete ionic equation lists all the ions present in the solution before and after the reaction. It provides a clearer picture of the reaction's participants but can be simplified by eliminating the spectator ions—those that do not participate in the chemical change.

The resulting simplified version is known as the net ionic equation and it highlights only those ions that actively engage in the formation of the precipitate. In the provided exercise, the net ionic equation for the reaction between mercury(II) nitrate and sodium chloride reveals the actual chemical change by showing how mercury ions combine with chloride ions to form the insoluble mercury(I) chloride.

Spectator ions might seem like passive participants in chemical reactions, but recognizing them is crucial for simplifying complex ionic equations. They are ions that are present in the reaction mixture but do not take part in the actual chemical reaction — in essence, they 'watch' the reaction happen without getting involved.

The identification of spectator ions allows chemists to focus on the active participants of a reaction. By cancelling out these inactive ions, one can write a net ionic equation that is much simpler and directly represents the essence of the chemical process. In typical precipitation or neutralization reactions, such as the removal of mercury ions with chloride ions, spectator ions like sodium (Na+) and nitrate (NO3-) do not undergo any change and are thus omitted from the net ionic equation, streamlining the depiction of the reaction and clarifying the outcome.