Problem 23 - A Complete Resource Book in Chemistry for JEE Main

Question

Which is not dissolve by dil HCl? (a) \(\mathrm{MnS}\) (b) \(\mathrm{ZnS}\) (c) \(\mathrm{BaSO}_{4}\) (d) \(\mathrm{BaSO}_{3}\)

Step-by-Step Solution

Answer

Barium sulfate (bBaSO_4b) does not dissolve in dil HCl.

Step 1: Understanding Solubility

To determine which compound is not dissolved by dilute hydrochloric acid (dil HCl), we need to consider the solubility of the given compounds in acids. Generally, sulfides (aSbS) of metals are not highly soluble in dilute acids, except for those belonging to the alkaline earth metals and certain heavy metals.

Step 2: Analyzing Each Compound

1. bMnSb: Manganese sulfide (bMnSb) is soluble in dilute acidic solutions. 2. bZnSb: Zinc sulfide (bZnSb) is generally insoluble in dilute hydrochloric acid. 3. bBaSO_4b: Barium sulfate (bBaSO_4b) is highly insoluble in water and does not dissolve in dilute acids. 4. bBaSO_3b: Barium sulfite (bBaSO_3b) can dissolve in dilute hydrochloric acid by releasing sulfur dioxide (bSO_2b) gas.

Step 3: Conclusion

Upon analyzing the compounds, bBaSO_4b is the compound that does not dissolve in dilute hydrochloric acid (dil HCl) due to its extremely low solubility in water and acids.

Key Concepts

Barium Sulfate Solubility

Barium sulfate, also represented as \( \mathrm{BaSO}_4 \), is an intriguing compound when it comes to solubility. It is known for its extremely low solubility in water and many acids, including dilute hydrochloric acid. This insolubility is due to the strong lattice energy in its crystalline structure, which is hard to overcome in a solution.

As a sparingly soluble compound, \( \mathrm{BaSO}_4 \) forms when a barium ion meets a sulfate ion in a solution and precipitates out almost immediately. This property makes it a popular component in medical radiology where it is used in contrast agents, allowing doctors to examine the gastrointestinal tract. When thinking about solubility rules, barium sulfate serves as a textbook example of a salt with ions that are so tightly arranged that typical solvents like water or dilute acids cannot dissolve it effectively.

• Highly resistant to dissolution in water.
• Unreactive to dilute acids such as HCl.
• Commonly used in medical imaging for its inert nature.

Acid-Base Reactions

Acid-base reactions are a fundamental category of reactions which involve the transfer of protons. In the context of dissolving compounds using acids, we often rely on these reactions to predict whether a substance will dissolve. For instance, certain sulfide compounds like manganese sulfide \( \mathrm{MnS} \) can dissolve in dilute HCl, owing to the release of hydrogen sulfide gas.

Such reactions can be understood through the Bronsted-Lowry acid-base theory, where an acid donates protons and a base accepts protons. When an acid like \( \mathrm{HCl} \) interacts with sulfides, it donates protons that react with the sulfide ions \( \mathrm{S}^{2-} \), aiding in the dissolution of the compound through a series of proton-transfer processes.

• Acids donate protons in reactions.
• Sulfide ions often react to release hydrogen sulfide gas.
• Effective in dissolving many sulfide compounds.

Sulfide Compounds

Sulfide compounds, denoted as \( \mathrm{MS} \) where \( \mathrm{M} \) is a metal, are a class of compounds that exhibit a range of behaviors in acidic solutions. These compounds involve sulfide ions \( \mathrm{S}^{2-} \), which typically do not dissolve easily in water but show varied solubility in acids.

Zinc sulfide \( \mathrm{ZnS} \), for example, is generally insoluble in dilute acids like HCl, owing to its stable ionic structure. However, some sulfides, particularly those of transition metals, may interact with acids to produce hydrogen sulfide gas, which characterizes the solubilization of such sulfides in acidic media. This reaction not only involves dissolution but also the evolution of gas, which is a significant indicator in qualitative analysis.

• Often insoluble in water but can dissolve in acids.
• May release hydrogen sulfide gas upon reaction with acids.
• Have varied solubility depending on the metal involved.