Problem 15 - Chemistry The Central Science In Si Units

Question

We have learned in this chapter that many ionic solids dissolve in water as strong electrolytes; that is, as separated ions in solution. Which statement is most correct about this process? (a) Water is a strong acid and therefore is good at dissolving ionic solids. (b) Water is good at solvating ions because the hydrogen and oxygen atoms in water molecules bear partial charges. (c) The hydrogen and oxygen bonds of water are easily broken by ionic solids.

Step-by-Step Solution

Answer

The correct statement is (b). Water is effective at solvating ions due to its polar nature.

Step 1: Analyzing Statement (a)

Statement (a) claims that water is a strong acid, which helps it dissolve ionic solids. However, this statement is not accurate. Water is not classified as a strong acid; instead, it is a neutral solvent with a pH of 7 at standard conditions. The dissolution of ionic solids in water is not due to its acidic properties.

Step 2: Evaluating Statement (b)

Statement (b) suggests that water is effective at solvating ions because its molecules have partial charges. This statement is correct. Water molecules are polar, with oxygen having a partial negative charge and hydrogen having a partial positive charge. This polarity allows water to surround and solvate ions effectively, facilitating the dissolution of ionic compounds.

Step 3: Reviewing Statement (c)

Statement (c) asserts that the bonds within water are easily broken by ionic solids. This is incorrect. The covalent bonds between hydrogen and oxygen within a water molecule are stable and not broken during the dissolution of ionic solids. Instead, water acts as a solvent by surrounding the ions and separating them from the solid lattice.

Key Concepts

Ionic Solids

Ionic solids are fascinating and integral components in chemistry. These are substances composed of positive and negative ions. They are arranged in a highly structured and repeating pattern called a lattice. The forces holding these ions together are strong electrostatic attractions known as ionic bonds. It is this strong bonding that gives ionic solids distinct characteristics.

A few notable traits of ionic solids include:

• High Melting and Boiling Points: The strong ionic bonds make it hard for these solids to break apart, even under high temperature.
• Brittleness: Although they are strong, ionic solids tend to shatter when stress is applied, as the like charges align and repel each other.
• Electrical Conductivity: As solids, they don't conduct electricity. But when they dissolve in water or melt, they break into ions and can conduct electricity as strong electrolytes.

When ionic solids dissolve in water, their lattice breaks, and the positive and negative ions disperse. This dispersion is crucial in processes like conducting electricity in solutions.

Polar Molecules

Polar molecules have a unique trait where there is an uneven distribution of charge. A fantastic example of a polar molecule is water. In water, the oxygen atom holds a partial negative charge, while the hydrogen atoms have partial positive charges. The structure of these molecules causes an effective electrical imbalance across them.

Here’s why the polarity is important:

• Interaction with Ions: The partial charges allow polar molecules to interact with ions and other polar molecules effectively.
• Formation of Hydrogen Bonds: These special interactions occur because of the attraction between partial charges.
• Solubility Capabilities: Polar molecules, such as water, are excellent solvents for other polar substances and ionic compounds.

Because of their ability to stabilize ions in solution, polar molecules like water play essential roles in processes such as solvation, which is critical for many chemical reactions.

Solvation Process

The solvation process is where a solvent, often water, surrounds and interacts with solute molecules or ions. Think of it as the solvent's welcoming hug to the solute, breaking it down.

This process involves a series of steps:

• Attraction: The partially charged ends of the polar molecules, like water, attract the oppositely charged ions in the solute.
• Separation: This attraction helps pull the ions, previously locked in a solid lattice, into the solution.
• Stabilization: Once in the solution, the solvent surrounds the ions, keeping them apart and stabilizing the solution.

This interaction is crucial for dissolving ionic compounds in solvents and forms the basis for many chemical processes, including reactions in living organisms and industrial applications. The solvation process makes it possible for substances to interact in solution, enabling electricity conduction and reaction facilitation in aqueous environments.