Rank the following molecules from least water soluble to most water soluble. Explain your reasoning.
(b) LiCl

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Step 1: Begin by understanding the concept of water solubility. Water solubility is influenced by the ability of a molecule to interact with water molecules through hydrogen bonding, ion-dipole interactions, or polarity. Ionic compounds, such as salts, tend to dissolve well in water due to strong ion-dipole interactions.

Step 2: Analyze the given molecule, LiCl. Lithium chloride (LiCl) is an ionic compound composed of Li⁺ (lithium ion) and Cl⁻ (chloride ion). Ionic compounds generally exhibit high water solubility because water molecules can stabilize the ions through ion-dipole interactions.

Step 3: Consider the size and charge density of the ions. Lithium ion (Li⁺) is a small cation with a high charge density, which enhances its ability to interact with water molecules. Chloride ion (Cl⁻) is a larger anion but still interacts effectively with water due to its negative charge.

Step 4: Compare LiCl to other molecules in the ranking (if provided). If the other molecules are nonpolar or have weaker interactions with water, LiCl will likely be more water soluble due to its ionic nature and strong ion-dipole interactions.

Step 5: Conclude that LiCl is expected to be highly water soluble due to its ionic nature and the strong interactions between its ions and water molecules. Rank it accordingly in the list from least to most water soluble.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Polarity of Molecules

Polarity refers to the distribution of electrical charge over the atoms in a molecule. Polar molecules, which have a significant difference in electronegativity between their atoms, tend to dissolve well in water due to their ability to form hydrogen bonds with water molecules. In contrast, nonpolar molecules do not interact favorably with water, leading to lower solubility.

Ionic Compounds and Solubility

Ionic compounds, such as LiCl, consist of positively and negatively charged ions. These compounds typically have high solubility in water because the polar water molecules can effectively surround and separate the ions, overcoming the ionic bonds holding them together. The solubility of an ionic compound is influenced by the strength of the ionic bonds and the hydration energy of the ions.

Hydration Energy

Hydration energy is the energy released when ions are surrounded by water molecules. This process stabilizes the ions in solution and is a key factor in determining the solubility of ionic compounds. A higher hydration energy generally leads to greater solubility, as it compensates for the energy required to break the ionic bonds in the solid state.

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