What is Solute in Chemistry | Definition, Types, Examples

Definition of Solute

solute in chemistry
  • A substance that is dissolved in a solution is called a solute.
  • A solute is defined as the substance that is dissolved in a solution.
  • In chemistry, a solute is the substance dissolved in a solvent or the part of a chemical solution present in the smaller amount.
  • A solute that can dissolve in a given solvent is said to be soluble in that solvent.
  • A solute that cannot dissolve a given solvent is said to be insoluble in that solvent.

The term “solute” comes from the Latin word solvere, which means “to loosen.” The words “solvent” and “dissolve” also derive from the same word.

Other Definitions

For solutions of fluids, the solvent is present in greater amounts than the solute. Concentration is a measurement of the amount of solute present in a chemical solution regarding the amount of solvent.

Although the solute holds a minor amount in the solution, as compared to the solvent. But there is a condition in the solution called saturation, in which the solvent cannot dissolve any more solutes.

The quantity of solvent in a liquid solution is greater than the amount of solute. Salt and water are two of the most common examples of solutes in our daily lives. Since salt dissolves in water, it is the solute.

Solutes in Saturated and Unsaturated Solution

When a solution dissolves solutes as much as possible at a particular temperature, is called a saturated solution. In simple terms, it can also be defined as, at a given temperature when no more solute can dissolve itself in the solution, it is a saturated solution.

When the quantity of solutes is not the same as the saturation level but less than that, it is an unsaturated solution. A solute is typically a solid dissolved into a liquid.

Salt is the solute that dissolves to form a saline solution in water, the solvent. On the other hand, water vapor is considered an air solute because nitrogen and oxygen are present in the gas at much higher concentration levels.

When a solute is dissolved in a solution, that solution’s chemical and physical properties are changed accordingly. Sometimes, a solvent may be composed of different solutes. When a water-soluble ionic compound is dissolved in water, this compound gets separated into its aqueous ions.

Then this ionic compound is the solute of that solution. When a covalent compound is dissolved in a solution, it is separated into its molecules.

Solutes can be either Polar or Nonpolar

Polar solutes can be dissolved in polar solvents, whereas nonpolar solutes can be dissolved in nonpolar solvents.

Solutes usually have higher boiling points compared to solvents. The solubility of a solute may depend on the temperature, type of solvent that is used, and the surface area of the solute compound.

Therefore, we can increase the solubility of the solute in a suitable solvent by increasing the surface area.

Forms of Solute

A solute can take many forms. It may be in the form of a gas, a liquid, or a solid. The solvent, or material that dissolves the solute, separates the solute molecules and distributes them evenly.

In fluid solutions, the amount of solvent present is greater than the amount of solute. One best example of solute in our day-to-day activity is salt and water. Salt dissolves in water, and therefore, salt is the solute.

Solvation

Mixing a solute and a solvent resulting in dissolving the solutes, which is also known as solvation. Concentration describes the amount of solute in a solvent or solution.

For example, the concentration 0.1M HCl describes a solution consisting of 0.1 moles of hydrochloric acid per liter of solution.

Examples of Solute

Usually, a solute is a solid that is dissolved into a liquid. An everyday example of a solute is salt in water. Salt is the solute that dissolves in water, the solvent, to form a saline solution.

On the other hand, water vapor is considered a solute in air because nitrogen and oxygen are present in much larger concentration levels in the gas.

Salt in Seawater

  • Salt is the solute, and water is the solvent in seawater.
  • The salt, NaCl, is an ionic compound where the negatively charged chloride ion is attracted by the slightly positively charged hydrogen atom of water. A similar attraction occurs between sodium and oxygen atoms.
  • This attraction causes the breakdown of NaCl into smaller particles which are then dispersed throughout the water.
  • The range of solubility and time period depends on the surface area of the solute particle.
  • Thus, coarse salts dissolve to a lesser extent than finer salts with a larger surface area.
  • Once all the salt is dissolved, no salt crystals will be visible in the solution.

Protons in the Cytoso

  • Protons or H+ are present in the cytoplasm of a cell that helps to maintain the pH of the solution.
  • These protons are attracted by the oxygen atom of water molecules and thus play an essential role in the transmembrane transport of molecules.
  • The membranes are permeable to water but not to the protons. As a result water molecules can freely across the membrane.
  • Due to the attraction between the water molecules and protons, a proton motive force is created.
  • The proton motive force can then be used for the transport of a variety of substances across the membrane.

The solutes examples are listed below with the corresponding solution

SolutionsCorresponding Solute in the Solution
Brass AlloyZinc in Copper
AmalgamMercury in Silver
Antifreeze in RadiatorEthylene Glycol in Water
Carbonated BeveragesCO2 in Water
Air in AtmosphereMany Gases in Nitrogen
BronzeTin Dissolved in Copper
Sugar WaterSugar Dissolved in Water
Alcoholic DrinksAlcohol Dissolved in Water
SaltwaterSalt Dissolved in Water

Characteristics of Solute

  • A solution is a homogeneous mixture of two or more substances.
  • The particles of solute in a solution cannot be seen by the naked eye.
  • A solution does not allow beams of light to scatter.
  • A solution is stable.
  • The solute from a solution cannot be separated by filtration (or mechanically).
  • It is composed of only one phase.

Types of Solute

types of solute

Homogeneous means that the components of the mixture form a single phase. Heterogeneous means that the components of the mixture are of different phase.

The properties of the mixture including concentration, temperature, and density can be uniformly distributed through the volume but only in the absence of diffusion phenomena or after their completion. The major types of solutes are :

  • Gaseous
  • Liquid
  • Solid

Gaseous

If a solvent is a gas, then only gases are dissolved under a given set of conditions. An example of a gaseous solution is air such as oxygen and other gases dissolved in nitrogen.

Liquid

If the solvent is a liquid, then almost, liquids, and solids can be dissolved. Here are some examples :

Gas in Liquid

gas in liquid
  • Oxygen in water.
  • Carbon dioxide in water.

Liquid in Liquid

liquid solute in liquid
  • The mixing of two or more substances of the same chemistry but different concentrations to form a constant.
  • Alcoholic beverages are basically solutions of ethanol in water.

Solid in Liquid

solid in liquid
  • Sucrose (sugar) in water.
  • Sodium chloride (NaCl) (salt) in water.

Solid

If the solvent is solid, then gases, liquids and solids can be dissolved.

Gas in Solids

gas in solid
  • Hydrogen dissolves rather well in metals, especially in palladium.

Liquid in Solid

liquid in solid
  • Mercury in gold, forming an amalgam.
  • Water in solid salt or sugar, forming moist solids.
  • Hexane in paraffin wax.

Solid in Solid

solid solute in solid solvent
  • Steel, basically a solution of carbon atoms in a crystalline matrix of iron atoms.
  • Alloys like bronze and many others.
  • Polymers containing plasticizers.

Ionic Solutes

  • All solutes separate into individual particles when they dissolve, but the particles are different for ionic and covalent compounds. Ionic solutes separate into individual ions. Covalent solutes separate into individual molecules.
  • Salt, or sodium chloride (NaCl), is an ionic compound. When it dissolves in water, it separates into positive sodium ions (Na+) and negative chloride ions (Cl). The negative oxygen ends of water molecules attract the positive sodium ions, and the positive hydrogen ends of water molecules attract the negative chloride ions. These forces of attraction pull the ions apart.

Covalent Solutes

  • Covalent solutes separate into individual molecules.
  • The sugar glucose is a covalent compound. When sugar dissolves in water, it forms individual glucose molecules (C6H12O6). You can see how this happens in the Figure below. Sugar is polar like water, so sugar molecules also have positive and negative ends. Forces of attraction between oppositely charged ends of water and sugar molecules pull individual sugar molecules away from the sugar crystal. Little by little, the sugar molecules are separated from the crystal and surrounded by water.

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