Question

Which of the following on reaction with \(\mathrm{H}_{2} \mathrm{~S}\) does not produce metallic sulphide? (a) \(\mathrm{CdCl}_{2}\) (b) \(\mathrm{ZnCl}_{2}\) (c) \(\mathrm{CoCl}_{2}\) (d) \(\mathrm{CuCl}_{2}\)

Short answer

Each forms an insoluble sulfide. Verify problem context or error.

Step-by-step solution

Understanding the Question

The problem asks which of the given compounds does not form a metallic sulfide upon reaction with hydrogen sulfide (\(\mathrm{H}_{2} \mathrm{S}\)). We need to identify the compound that does not form a sulfide precipitate.

Reviewing Metal Sulfide Solubility

To solve this, we should know which metal sulfides are insoluble. For many metals like Cd, Zn, and Cu, the sulfide formed with \(\mathrm{H}_{2} \mathrm{S}\) is insoluble, causing a precipitate. These sulfides are generally insoluble in water.

Evaluating Each Option

- **Option (a): \(\mathrm{CdCl}_2\)** - Forms \(\mathrm{CdS}\), which is insoluble.- **Option (b): \(\mathrm{ZnCl}_2\)** - Forms \(\mathrm{ZnS}\), which is insoluble.- **Option (c): \(\mathrm{CoCl}_2\)** - Typically forms \(\mathrm{CoS}\), which is also insoluble.- **Option (d): \(\mathrm{CuCl}_2\)** - Generally forms \(\mathrm{CuS}\), which is insoluble.

Identifying the Exception

All the options form insoluble sulfides upon reaction with \(\mathrm{H}_{2} \mathrm{S}\), which initially seems incorrect about the question. Upon verification, none of these correctly fit the criteria as each of these will produce a metallic sulfide. We need to consider the context or if any condition or error exists, as all should behave alike.

Key concepts

Hydrogen Sulfide Reactions

Hydrogen sulfide, or \(\mathrm{H}_{2} \mathrm{S}\), is a colorless gas known for its characteristic smell of rotten eggs. It reacts with various metal salts to form metal sulfides. This process is commonly referred to as a precipitation reaction where the metal ions in the solution react with hydrogen sulfide. The result is typically a solid sulfide that precipitates out of the solution. This transformation is particularly interesting because it involves the donation of sulfur ions from hydrogen sulfide to ions from the metal salt. Commonly used in laboratory settings, this reaction helps to identify and separate metal ions through their unique sulfide formations. Understanding the principles behind hydrogen sulfide reactions is crucial for both analytical chemistry and industrial applications. The formation of metal sulfides can be affected by factors including the concentration of hydrogen sulfide, the type of metal ion, and the specific conditions of the reaction.

Precipitation Reactions

Precipitation reactions occur when two solutions combine to form an insoluble solid known as a precipitate. This solid forms when the product of the ion concentrations in the solution exceeds the solubility product constant of the compound. It's a useful method in analytical chemistry to isolate and identify various components.The interaction of metal salts with \(\mathrm{H}_{2} \mathrm{S}\) to create metal sulfides is a classic example of a precipitation reaction. For those studying chemistry, recognizing the signs of these reactions is key. You'll typically observe a "cloudiness" in the solution as the precipitate forms, indicating that a new solid substance has come into existence. This kind of reaction is essential not only in the laboratory but also in understanding natural processes, such as formation of ores. The unique identities of the metal sulfides can often be determined by their colors and solubility properties.

Solubility of Sulfides

The solubility of metal sulfides varies widely depending on the specific metal cation involved. In general, most metal sulfides are insoluble in water, making them ideal candidates for separation via precipitation reactions. For example, sulfides of metals such as cadmium, zinc, and copper are characteristically insoluble.Understanding sulfide solubility is crucial because it dictates whether a precipitate will form when a metal salt reacts with \(\mathrm{H}_{2} \mathrm{S}\). Solubility charts and rules exist to help predict these outcomes, showing that sulfides of metals like iron, nickel, and cobalt also tend to be insoluble. However, there are exceptions to these rules. Some sulfides can become soluble under specific conditions, like in the presence of strong acidic or basic environments. Therefore, predicting the outcome of a reaction requires both a look at general solubility trends and the specific chemical environment.

Insoluble Compounds

Insoluble compounds, including many metal sulfides, are those that do not dissolve to a significant extent in water. The formation of insoluble compounds is an important concept in precipitation reactions and helps chemists to isolate and study different substances. When \(\mathrm{H}_{2} \mathrm{S}\) is reacted with many metal chlorides, insoluble metal sulfides typically form. These reactions are not only theoretically intriguing but also hold practical significance. For instance, in wastewater treatment, the precipitation of insoluble sulfides can help to remove heavy metals from solution, making the water safer for discharge.Understanding the nature of insoluble compounds requires an appreciation of chemical bonding and the forces at play within different molecules or ionic compounds. While many compounds will dissolve in water under standard conditions, those considered insoluble are defined by their inability to dissociate and dissolve, leading to the formation of a solid precipitate.