Problem 101 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statement is not correct regarding the properties of ionic compounds? (a) ionic compounds have high melting and boiling points (b) their reaction velocity in aqueous medium is very high. (c) ionic compounds in their molten and aqueous solutions do not conduct electricity. (d) they are highly soluble in polar solvents.

Step-by-Step Solution

Answer

Statement (c) is incorrect.

Step 1: Understand the properties of ionic compounds

Ionic compounds are formed from the electrostatic attraction between cations and anions. This gives them several characteristic properties, such as high melting and boiling points due to the strong ionic bonds. These compounds also conduct electricity when molten or dissolved in water, as the ions are free to move and carry charge.

Step 2: Analyze each statement

- (a) This statement is correct: Ionic compounds do have high melting and boiling points due to the strong forces holding the ions together. - (b) This statement is somewhat correct: Ionic compounds can react in aqueous solutions, and the presence of free ions often means reactions can be rapid. - (c) This statement is incorrect: Ionic compounds do conduct electricity in molten state or when dissolved in water, as the ions are free to move. - (d) This statement is correct: Ionic compounds are generally soluble in polar solvents like water, which can stabilize the separated ions.

Step 3: Identify the incorrect statement

Based on the analysis, option (c) is incorrect because it states that ionic compounds do not conduct electricity when molten or in aqueous solutions, which opposes the known property of ionic compounds.

Key Concepts

properties of ionic compounds

Ionic compounds are unique and fascinating, primarily due to the strong electrostatic forces that bind them together. These forces are the result of interactions between positive ions, known as cations, and negative ions, known as anions. This connection results in a number of properties whose understanding is essential in chemistry.

Some of the hallmark properties of ionic compounds include:

• High melting and boiling points: The strong ionic bonds need a lot of energy to break, which is why ionic compounds have high melting and boiling points.
• Crystalline structure: Ionic compounds often form crystal lattice structures, which is a characteristic arrangement providing them with a solid structure.
• Solubility in water: Most ionic compounds dissolve in polar solvents like water, where the solvent molecules surround and separate the ions.
• Electrical conductivity: When molten or dissolved in water, ionic compounds conduct electricity, an important property that we will explore further in the next sections.

The nature of these properties makes ionic compounds crucial in various applications, from table salt consumption to industrial processes.

conductivity of ionic compounds

When discussing the conductivity of ionic compounds, it's important to distinguish between their solid state and when they are molten or dissolved in a solution. In their solid state, ionic compounds do not conduct electricity. This is because the ions are locked in a rigid lattice structure and cannot move freely.

Once the ionic compounds are molten or in an aqueous solution, their conductivity changes significantly:

• Free ions: In the molten state, heat energy overcomes the crystal lattice, allowing ions to move freely. Similarly, in aqueous solutions, water molecules separate the ions.
• Movement and charge: Free ions allow electrical current to pass through the substance as they move towards the electrodes when a potential difference is applied.

Thus, ionic compounds exhibit excellent electrical conductivity in states where ions are free, making them useful in electrochemical applications and batteries.

solubility of ionic compounds

The solubility of ionic compounds is a key property that allows them to participate in many chemical reactions, especially in aqueous solutions. The reason behind their solubility primarily lies in the interactions with polar solvents, like water.

Here's how solubility works:

• Polar nature: Water is a polar solvent, meaning it has a partial positive charge on one side and a partial negative charge on the other, which attracts and stabilizes the ions in an ionic compound.
• Hydration: When an ionic compound dissolves, water molecules surround the ions, a process known as hydration, which helps separate them from the lattice structure.
• Solubility variation: Not all ionic compounds dissolve equally well; factors like lattice energy and the size of ions affect solubility.

This property makes ionic compounds versatile for use in various fields, from biological systems where water is a universal solvent to industrial applications.

melting and boiling points of ionic compounds

Ionic compounds are known for their strong ionic bonds, which result in high melting and boiling points. But what is behind these high thermal thresholds?

First, it's important to recognize:

• Strong ionic bonds: The electrostatic forces between oppositely charged ions are very strong, which means a lot of energy is required to break these bonds.
• Lattice structure: The ions are arranged in a highly ordered crystal lattice that adds stability and contributes to the high energy required for melting and boiling.

These factors explain why ionic compounds remain solid at room temperature and require substantial heating to turn into liquid or gas. In practical applications, this means ionic compounds can withstand high-temperature processes without decomposing, making them valuable in material science and engineering.