Question

Which of the following combinations would be likely to form a minimum-boiling azeotrope? 1\. Water and chlorobenzene 2\. Water and nitric acid 3\. Water and hydrogen peroxide 4\. Water and acetone

Short answer

The correct combination that would likely to form a minimum-boiling azeotrope is Water and Acetone (option 4), due to the significant difference in polarity between the two components.

Step-by-step solution

Understand Azeotropes

An azeotrope is a mixture of two or more liquids with a constant boiling point and composition throughout the distillation process. Azeotropes can be classified as either minimum-boiling or maximum-boiling. A minimum-boiling azeotrope is formed when the azeotropic mixture has a lower boiling point than either of its components. In general, minimum-boiling azeotropes are formed by substances with significant differences in their polarity.

Examine Each Combination

Now let us examine each combination of liquids to determine which one is likely to form a minimum-boiling azeotrope. 1. Water and Chlorobenzene: Water is a polar molecule while chlorobenzene is a moderately polar molecule. The difference in polarity is not significant enough to form a minimum-boiling azeotrope. 2. Water and Nitric Acid: Water and nitric acid are both polar molecules and have a strong interaction with each other due to hydrogen bonding. This strong interaction would likely result in a maximum-boiling azeotrope rather than a minimum-boiling azeotrope. 3. Water and Hydrogen Peroxide: Water and hydrogen peroxide are both polar molecules with strong hydrogen bonding. Just like water and nitric acid, this combination will likely form a maximum-boiling azeotrope. 4. Water and Acetone: Water is a polar molecule, and acetone is a polar solvent with a significant difference in polarity compared to water. This combination meets the criteria for a minimum-boiling azeotrope due to the difference in the polarity of the components.

Identify the Correct Combination

Based on our analysis of each combination, it is most likely that the combination of Water and Acetone will form a minimum-boiling azeotrope. So, the correct answer is option 4: Water and Acetone.

Key concepts

Azeotropes

Azeotropes are fascinating mixtures because they behave differently from typical mixtures. In an azeotrope, two or more liquids combine in such a way that their proportions remain constant during boiling. This means, even when you boil the mixture, the vapor has the same composition as the liquid.
There are two main types of azeotropes: minimum-boiling and maximum-boiling. Minimum-boiling azeotropes have a boiling point lower than any of the individual components. This usually happens when the components have a significant difference in polarity, leading to less stable hydrogen bonding and easier vaporization. Maximum-boiling azeotropes, however, have a boiling point higher due to strong intermolecular attractions.
Understanding azeotropes is crucial for industries that rely on distillation, such as oil refining and chemical manufacturing, because they present unique challenges in separation processes.

Polarity

Polarity is a primary concept in chemistry that helps explain how and why molecules interact. It's all about the distribution of electrical charge across a molecule.
Molecules with uneven charge distribution are called polar molecules. They have positive and negative ends, like a magnet. For example, water is a polar molecule because its oxygen atom holds more negative charge while its hydrogen atoms hold positive charge. Nonpolar molecules, on the other hand, have more equal charge distribution.
The polarity of a molecule affects everything from boiling points to solubility. In the case of azeotropes, a significant difference in polarity between components can lead to the formation of a minimum-boiling azeotrope. Polarity is a critical factor in determining how molecules will behave when mixed or subjected to changes in temperature.

Mixtures

Mixtures are combinations of two or more substances where each substance retains its own chemical properties. Unlike compounds, the substances in mixtures are not chemically bonded.
Mixtures can either be homogeneous or heterogeneous. Homogeneous mixtures, also known as solutions, have uniform composition throughout. Examples include saltwater or air. Heterogeneous mixtures, like sand in water, have distinct parts that can often be separated physically.
When discussing azeotropes, we focus on homogeneous mixtures. These unique mixtures have constancy in composition during the boiling process, making them behave as a single substance. This aspect of mixtures is particularly important in understanding distillation processes in chemistry.

Boiling Point

The boiling point is the temperature at which a substance changes from a liquid to a gas. It's an important characteristic because it helps identify substances and understand their properties.
In mixtures, the boiling point can change due to interactions between different components. In azeotropes, this can result in a constant boiling point distinct from the pure substances involved. For a minimum-boiling azeotrope, the boiling point is lower than each component, often due to weak intermolecular forces caused by differences in polarity.
Being aware of boiling points is crucial in processes like distillation, where separating components of a mixture is necessary. Knowing how different substances interact to affect boiling point helps chemists and engineers in designing efficient separation methods.