Question

The reaction of \(\mathrm{H}_{2} \mathrm{O}\) with \(\mathrm{X}\) does not liberate gaseous product. Which of the following is \(X\) ? (a) \(\mathrm{PbO}_{2}\) (b) \(\mathrm{KMnO}_{4} / \mathrm{H}^{+}\) (c) \(\mathrm{PbS}\) (d) \(\mathrm{Cl}_{2}\)

Short answer

The substance \(X\) is \(\mathrm{PbS}\) (option c).

Step-by-step solution

Analyze each candidate

We need to determine which substance reacts with \(\mathrm{H}_{2} \mathrm{O}\) without liberating a gaseous product. We'll analyze each option:(a) \(\mathrm{PbO}_2\) - Lead(IV) oxide can act as an oxidizing agent, but in water, it does not typically liberate any gaseous products.(b) \(\mathrm{KMnO}_4 / \mathrm{H}^{+}\) - Potassium permanganate in acidic conditions can react and potentially release gases like \(\mathrm{O}_2\).(c) \(\mathrm{PbS}\) - Lead(II) sulfide is generally insoluble in water and less reactive, making it unlikely to liberate a gas.(d) \(\mathrm{Cl}_2\) - Chlorine gas will definitely release \(\mathrm{HCl}\) when reacting with water.

Identify which reaction doesn't release gas

Considering the analysis above:- \(\mathrm{PbO}_2\) in water doesn't typically release gases.- \(\mathrm{KMnO}_4 / \mathrm{H}^{+}\) may produce \(\mathrm{O}_2\) gas.- \(\mathrm{PbS}\) is inert in water, so it does not react to release gas.- \(\mathrm{Cl}_2\) will release \(\mathrm{HCl}\), a gaseous product.Therefore, \(\mathrm{PbS}\) (option c) reacts without gaseous product.

Conclusion

The compound that reacts with \(\mathrm{H}_2 \mathrm{O}\) without liberating a gaseous product is \(\mathrm{PbS}\). It is relatively stable and does not readily decompose or react to form a gas in water.

Key concepts

Insolubility of PbS

Lead(II) sulfide, or PbS, is a chemical compound recognized for its remarkable low solubility in water. This insolubility is a critical characteristic that affects its chemical behavior in reactions. When introducing PbS to water, no substantial reaction occurs, and it remains largely unchanged. There are a few reasons behind this. Primarily, PbS forms because of the strong ionic bonding between the lead and sulfur ions, which aren't easily disrupted by water molecules.
As a result, when considering reactions such as those with water, PbS doesn't release gas because its insolubility and chemical stability impede any breakdown or gas evolution. In laboratory settings and practical applications, this property ensures that when PbS is used, it remains a stable compound.
Additionally, it's worth noting that PbS is a naturally occurring mineral known as galena. Galena's presence as an ore in nature underscores its stability and minimal reactivity, which engineers and chemists must account for when dealing with lead sulfide in environmental or industrial contexts.

Oxidizing Agents

Oxidizing agents are substances that gain electrons during a chemical reaction, causing another substance to lose electrons. This process is fundamental in redox reactions, where one substance is oxidized, and another is reduced. Some of the most effective oxidizing agents include oxygen ( \( O_2 \)), permanganate ( \( KMnO_4 \)), and chlorine ( \( Cl_2 \)).
When discussing oxidizing agents, it's essential to understand their ability to pull electrons away from other substances. In the context of the given exercise, options such as \( PbO_2 \) and \( KMnO_4/H^+ \) illustrate compounds that can act as oxidizing agents. For example, \( KMnO_4 \underwent \acidic \conditions \can \liberate \O_2 \gas \since \potassium \permanganate \breaks \down. \)
This makes it highly reactive, differentiating it from other compounds like \( PbS \) in scenarios where stability without gaseous product formation is required. Understanding these concepts can help students predict the behavior of compounds in chemical reactions.

Gaseous Products in Reactions

In chemical reactions, the formation of gaseous products can be a critical factor in understanding reaction types and outcomes. Gaseous products arise from the breakdown of reactants, often when a volatile compound forms, making the gas evolve from the solution. Recognizing which reactions generate gases helps predict and verify reaction conditions.
For the reactions evaluated in the exercise, \( Cl_2 \)with water releases hydrochloric acid gas ( \( HCl \)), further illustrating the production of gaseous substances under specific conditions. Similarly, oxidizing agents like \( KMnO_4/H^+ \) can liberate oxygen gas as a result of their decomposition.
Predicting gaseous outcomes in reactions is essential for laboratory safety, as well as understanding atmospheric and environmental chemistry. By comprehending which substances release gases and under what conditions, chemists and students can accurately anticipate and control reaction behavior.