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Ch.13 - Properties of Solutions
Chapter 13, Problem 15b

Indicate the type of solute–solvent interaction that should be most important in each of the following solutions: b. methanol (CH3OH) in water,

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Identify the polarities of the solute and solvent. Methanol (CH3OH) and water (H2O) are both polar molecules.
Recognize the ability of both methanol and water to form hydrogen bonds. Methanol has a hydroxyl group (-OH) capable of hydrogen bonding, and water has two hydrogen atoms and one oxygen atom suitable for hydrogen bonding.
Understand that similar types of intermolecular forces between solute and solvent enhance solubility. Since both methanol and water can form hydrogen bonds, they should dissolve well in each other.
Conclude that the most important type of solute-solvent interaction in a solution of methanol in water is hydrogen bonding.
Consider the general rule that 'like dissolves like' which supports the conclusion that hydrogen bonding is the dominant interaction in this solution due to the similar polar nature of both methanol and water.

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Key Concepts

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

Hydrogen Bonding

Hydrogen bonding is a strong type of dipole-dipole interaction that occurs when hydrogen is covalently bonded to highly electronegative atoms like oxygen or nitrogen. In the case of methanol (CH3OH) and water, both molecules can form hydrogen bonds due to the presence of hydroxyl (-OH) groups. This interaction significantly influences the solubility and properties of the solution.
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Polarity

Polarity refers to the distribution of electrical charge over the atoms in a molecule. Water is a polar solvent, meaning it has a partial positive charge on one side and a partial negative charge on the other. Methanol, being polar as well, interacts favorably with water, allowing for effective solvation and dissolution of methanol in water.
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Solvation

Solvation is the process by which solvent molecules surround and interact with solute particles. In the case of methanol in water, solvation occurs as water molecules surround methanol molecules, stabilizing them in solution. This interaction is crucial for understanding how solutes dissolve and the resulting properties of the solution.
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