Chapter 15: Problem 47

Ethanol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\), dissolves in water. So does magnesium chloride, \(\mathrm{MgCl}_{2}\). Yet there is a fundamental difference in the way these two substances dissolve. What is this fundamental difference?

Short Answer

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The fundamental difference in the way ethanol and magnesium chloride dissolve in water is that ethanol maintains its molecular structure and forms hydrogen bonds with water molecules due to its polar nature, while magnesium chloride dissociates into its constituent ions (Mg²⁺ and Cl⁻) that are then surrounded and stabilized by water molecules due to electrostatic interactions, resulting from its ionic nature.

Step by step solution

Identify the nature of the substances

Ethanol is an organic compound with a polar nature due to the presence of an hydroxyl group (OH) bonded to a carbon atom. On the other hand, magnesium chloride is an ionic compound, which consists of positively charged magnesium ions (Mg²⁺) and negatively charged chloride ions (Cl⁻).

Examine the dissolution process of Ethanol

When ethanol dissolves in water, it maintains its molecular structure because it forms hydrogen bonds with the water molecules. The polar nature of the ethanol molecule allows it to be attracted to the water molecules and be surrounded by them, leading to the dissolution process. The reaction can be represented as follows: \( \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} (\mathrm{aq}) + \mathrm{H}_{2} \mathrm{O} (\mathrm{l}) \rightarrow \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} (\mathrm{aq}) + \mathrm{H}_{2} \mathrm{O} (\mathrm{l}) \)

Examine the dissolution process of Magnesium Chloride

When magnesium chloride dissolves in water, it dissociates into its constituent ions - magnesium ions (Mg²⁺) and chloride ions (Cl⁻). The negatively charged oxygen atoms of water molecules surround the positively charged magnesium ions, while the positively charged hydrogen atoms of water molecules surround the negatively charged chloride ions. This process, known as hydration, results in the dissolution of the ionic compound in water. The reaction can be represented as follows: \( \mathrm{MgCl}_{2}(\mathrm{s}) + 4\, \mathrm{H}_{2} \mathrm{O} (\mathrm{l}) \rightarrow [\mathrm{Mg(H}_{2} \mathrm{O})_{4}]^{2+} (\mathrm{aq}) + 2\, \mathrm{Cl}^- (\mathrm{aq}) \)

Identify the fundamental difference

The fundamental difference in the way ethanol and magnesium chloride dissolve in water is that ethanol maintains its molecular structure and forms hydrogen bonds with water molecules, while magnesium chloride dissociates into its constituent ions that are then surrounded and stabilized by water molecules due to electrostatic interactions. This difference can be attributed to the polar nature of ethanol and the ionic nature of magnesium chloride.

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Ethanol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\), dissolves in water. So does magnesium chloride, \(\mathrm{MgCl}_{2}\). Yet there is a fundamental difference in the way these two substances dissolve. What is this fundamental difference?

Short Answer

Step by step solution

Identify the nature of the substances

Examine the dissolution process of Ethanol

Examine the dissolution process of Magnesium Chloride

Identify the fundamental difference

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