Problem 7 - A Complete Resource Book in Chemistry for JEE Main

Question

Which among the following is most soluble in alcohol? (a) \(\mathrm{KClO}_{4}\) (b) \(\mathrm{NaClO}_{4}\) (c) \(\mathrm{CsClO}_{4}\) (d) \(\mathrm{LiClO}_{4}\)

Step-by-Step Solution

Answer

Lithium perchlorate (LiClO_{4}) is the most soluble in alcohol.

Step 1: Analyzing Solubility Trends

Look at the solubility trends of different perchlorates in alcohol. Generally, the solubility of perchlorates in alcohol follows the trend of Lithium perchlorate being more soluble compared to other alkali perchlorates.

Step 2: Identifying Key Characteristics

Consider the properties of each compound. Compounds with smaller, less hydrated cations tend to be more soluble in non-aqueous solvents like alcohol. Lithium ion is smaller and less hydrated than the other alkali ions.

Step 3: Understanding Ionic Interactions

In alcohol, which is less polar than water, the smaller lithium ion forms stronger interactions with the solvent compared to larger cations. This enhances the solubility of its perchlorate salt.

Step 4: Selecting the Most Soluble Compound

Based on known empirical data and chemical principles regarding solubility, LiClO_{4} is the most soluble in alcohol among the given compounds.

Key Concepts

Perchlorates

Perchlorates are salts derived from perchloric acid, and they are commonly identified by their chemical formula which includes the anion \(\text{ClO}_4^-\). These compounds have fascinating chemical properties, particularly regarding their solubility in various solvents.
Solubility is influenced by the ionic character and the size of the cations associated with the perchlorate anion. Different metal perchlorates exhibit varying solubilities in solvents like alcohol due to differences in ionic interactions.
Some notable characteristics of perchlorates include:

• High solubility in water due to strong ionic interactions.
• Varied solubility in organic solvents like alcohol, dependent on the metal cation.

Understanding how perchlorates behave in solvents helps in predicting their solubility and potential applications in industries that require dissolution in alcohol.

Alcohol Solubility

The solubility of a compound in alcohol is a fundamental chemical property that is influenced by several factors. Alcohols are organic solvents that are less polar than water but can still interact with polar solutes through van der Waals forces and hydrogen bonding.
With perchlorates, the solubility in alcohol differs from that in water. This is due to the reduced polarity of alcohol, which affects how ions dissociate and interact. Certain perchlorates, such as lithium perchlorate, show impressive solubility levels in alcohol compared to others.
Key influences on alcohol solubility include:

• The size and charge density of the cation, with smaller ions like lithium exhibiting greater solubility.
• The degree of hydration of the ions; less hydrated ions are more soluble in less polar solvents.

These factors collectively determine the extent to which a given salt, like lithium perchlorate, will dissolve in alcohol.

Ionic Interactions

Ionic interactions are critical in determining the solubility of ionic compounds in solvents. These interactions are influenced by both the solvent's properties and the ions involved in the compound.
When discussing solubility in alcohol, it is important to consider:

• The dielectric constant of the solvent, which affects how well ions can be separated and surrounded by the solvent molecules.
• The size of the ion, with smaller ions such as lithium having stronger and more specific interactions due to their high charge density.

In the context of lithium perchlorate, its cation, lithium, forms significant interactions with the alcohol because of its small size and charge. These interactions are much stronger compared to larger cations like potassium, sodium, and cesium, which contribute less to solubility due to their weaker interaction with the solvent.

Lithium Ion Characteristics

Lithium ions possess unique characteristics that impact their behavior in solvents, particularly in alcohol. As the smallest alkali metal ion, lithium has a high charge density and a distinctive role in chemical solubility.
Some defining features of lithium ions include:

• Small ionic radius, which results in high charge density and stronger attraction to solvent molecules.
• Lower tendency to be heavily hydrated compared to larger alkali metal ions, which impacts its solubility in non-aqueous solvents like alcohol.
• Ability to form robust interactions with less polar solvents, enhancing solubility in such environments.

These attributes make lithium ions exemplary in increasing the solubility of their salts, such as lithium perchlorate, in polar organic solvents like alcohol, resulting in its greater solubility compared to other alkali perchlorates.