Chapter 7: Chemical Solutions

Chemical solutions are an essential part of the study of Chemistry and a fundamental topic to understand for the ENEM exam. In this chapter, we will explore the concept of chemical solutions, their characteristics, types, calculation formulas and practical examples.

Definition of Chemical Solutions

A chemical solution is a homogeneous mixture of two or more substances. The substance that is dissolved is called the solute and the substance in which the solute is dissolved is called the solvent. A solution can exist in any physical state: solid, liquid, or gas.

Types of Chemical Solutions

There are several types of chemical solutions, which are classified based on the physical state of the solvent and solute. Solutions can be solid, liquid or gaseous. For example, the air we breathe is a gaseous solution, while seawater is a liquid solution. Solid solutions include metal alloys such as bronze (a mixture of copper and tin).

Characteristics of Chemical Solutions

Chemical solutions have several distinct characteristics. They are homogeneous mixtures, which means that the composition is uniform throughout the solution. Also, solutions are stable, which means that the solute will not separate from the solvent if the solution is allowed to stand. Furthermore, the solute in a solution cannot be separated from the solvent by simple physical methods such as filtration.

Concentration of Chemical Solutions

The concentration of a chemical solution is a measure of the amount of solute present in a specific amount of solvent. There are several ways to express concentration, including molarity, molality, normality, mass percent, and mole fraction.

• Molarity (M): is the amount of solute (in moles) per liter of solution.
• Molality (m): is the amount of solute (in moles) per kilogram of solvent.
• Normality (N): is the amount of gram-equivalents of solute per liter of solution.
• Percent by mass (% by mass): is the mass of the solute divided by the total mass of the solution, multiplied by 100.
• Molar fraction (X): is the ratio of the number of moles of a substance to the total number of moles of all substances present.

Colligative Properties

Colligative properties are physical properties that depend on the number of solute particles in the solution rather than the nature of the solute. They include vapor pressure, boiling point elevation, freezing point depression, and osmotic pressure.

Practical Examples of Chemical Solutions

Chemical solutions are present in many aspects of our everyday lives. For example, seawater is a solution of water (solvent) with various salts (solutes). The air we breathe is a solution of several gases, including nitrogen, oxygen and carbon dioxide. Alcoholic beverages are solutions of alcohol in water. Even our blood is a solution, containing various substances dissolved in water.

In summary, chemical solutions are an essential part of our world and an important topic to understand for the ENEM exam. By mastering this topic, you will be well prepared to answer any question about chemical solutions that may appear on the test.