Solute

A solute is a substance that is dissolved in a solvent to form a solution. In an unsaturated solution, the concentration of solute is much lower than that of the concentration of solvent. Let’s take an example of a solution from day-to-day life—a solution of salt and water. In the given solution, salt acts as a solute while water acts as a solvent. So salt and water in the given example are solute and solvent examples, respectively. Here, we will study what is meant by solute, solute, and solvent examples in detail.

Solute and Solvent Definitions

To define solute and solvent, let us go through the following explanation. 

A homogeneous mixture consists of two or more substances in which a solute is dissolved into another solvent substance. The concentration of a solute in a solution is a measure of how much of the solute is dissolved in the solvent with respect to how much solvent is present.

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Characteristics of Solute

• A solution is a homogeneous mixture of two or more substances.

• The solute particles in a solution are not visible to the naked eye.

• A solution does not cause light beams to scatter.

• A solution is stable.

• The solute cannot be separated from the solution by filtration (or mechanically).

• It is composed of one phase only.

Types of Solute

Homogeneous means that a single phase is formed by the components of the mixture. Heterogeneous means that there are different phases formed by the different components of the mixture. 

The properties of the mixture, including concentration, temperature, and density, may be distributed uniformly through the volume, but only in the absence of or after the completion of diffusion phenomena. The three forms of solute are:

1. Gaseous

2. Liquid

3. Solid

1. Gaseous

In a given set of conditions, if the solvent is gas, then only gases can be dissolved as solutes, and the solution is said to be a gaseous solution. Example: Air is a gaseous solution, nitrogen being the most abundant gas in the air, and all the other gases such as oxygen are dissolved in it.

2. Liquid

If the solvent is liquid, then all the three forms of matter, solid, liquid, and gas, can be dissolved as a solute in it. Some solute and solvent examples are given below.

Gas in liquid

• Oxygen in water

• Carbon dioxide in water

Liquid in liquid

Alcoholic drinks are simply water-based ethanol solutions (where ethanol is a solute and water is a solvent.).

Solid in liquid

• Sugar solution (Sucrose is a solute added to water which is a solvent)

• Salt solution (Sodium chloride is a solute added to water)

Solid

If the solvent is solid, then all the three forms, solid, liquid, and gas, can be dissolved as a solute. Some solute and solvent examples are given below-

Gas in Solid

• Hydrogen gets readily dissolved or adsorbed on the surface of the metal, such as palladium.

Liquid in Solid

• An amalgam is formed when the mercury as a solute is dissolved in gold.

• Moist solids are formed when water is dissolved in solid salt or sugar.

Solid in Solid

• Iron, which is essentially a carbon atom solution in a crystalline matrix of iron atoms.

• Bronze-like alloys and several others.

• Plasticizer - containing polymers.

Examples of Solute and Solutions

A homogenous mixture of two or more substances in relative quantities that can be continuously varied up to what is known as the solubility limit. The word solution is usually applied to the liquid state of matter, but gas and solid solutions are also possible. A solution can be saturated or unsaturated. Saturated solutions are said to be those solutions where no more solute can be dissolved at a particular temperature. Unsaturated solutions are said to be those solutions where more solute can be dissolved at a given temperature. 

Did You Know?

We can calculate the concentration of solute and solvent by various methods. Two different units are defined to express the concentration.

Molarity is defined as the number of moles of solute present in 1L of solution. It is denoted by M. Molarity can be expressed as:

M= \[\frac{\text{No of moles of solute}}{\text{mass of solvent in kg}}\]  

Molality is defined as the number of moles of solute present in 1kg of solvent. It is denoted by m. Molality can be expressed as-

m= \[\frac{\text{No of moles of solute}}{\text{mass of solvent in kg}}\].