Characterize the following compounds as soluble or insoluble in water: (a) \(\mathrm{CaCO}_{3}\) (b) \(\mathrm{ZnSO}_{4}\) (c) \(\mathrm{Hg}\left(\mathrm{NO}_{3}\right)_{2},\) (d) \(\mathrm{HgSO}_{4}\) (e) \(\mathrm{NH}_{4} \mathrm{ClO}_{4}\).

When trying to understand solubility in water, there's a primary rule: 'Like dissolves like.' This means that polar substances tend to dissolve in polar solvents like water, while nonpolar substances are more likely to be soluble in nonpolar solvents.

Water's polarity enables it to interact with various chemical compounds. Ionic compounds, which consist of positively and negatively charged ions, are often soluble in water because the water molecules surround and stabilize the ions, separating them from each other.

Understanding this concept is crucial for many fields, including environmental science, where the solubility of pollutants in water can affect ecosystems, and in medicine, where solubility can influence drug efficacy.

The solubility of chemical compounds is not only determined by the nature of the solute and solvent but also by temperature and pressure. In general, solubility increases with temperature. However, there are exceptions, and some compounds may become less soluble as temperature rises.

For example, gases are more soluble in cold water, as seen with oxygen in natural water bodies, which is critical for aquatic life. Solubility can significantly impact reaction rates too, as only dissolved particles can react.

Let’s consider the periodic trends affecting solubility: Alkali metal salts and most ammonium salts are typically soluble, while silver and lead compounds are more likely to be insoluble unless they form certain complex ions, emphasizing the importance of context in predicting solubility.

Identifying soluble and insoluble compounds is integral for predicting the course of chemical reactions and for understanding the behavior of substances in different environments. A soluble compound, when placed in water, will dissociate and become surrounded by water molecules, forming a homogeneous mixture or solution. On the other hand, an insoluble compound will not noticeably dissolve and will often remain as a separate phase, such as a precipitate in a chemical reaction.

For practical applications, the knowledge of solubility is essential. This can range from a chemist who uses solubility rules to predict the outcomes of reactions to an industrial engineer who might need to know what chemicals will form scale in pipes and how to treat it.

Remembering key solubility rules can help predict solubility. All nitrates and alkali metal salts are soluble, as well as most ammonium, chloride, sulfate, and acetate compounds. Meanwhile, carbonates, sulfides, hydroxides, and phosphates are usually considered insoluble, with exceptions based on the metal they are attached to.