Solutions

What is a Solution?

Solutions are a homogeneous mixture of two or more substances.

Examples:

• Air: It is a mixture of gas in gas. Air is a homogeneous mixture of a number of gases. The two main constituents of gases are oxygen (21%) and Nitrogen (78%)

• Alloys: Alloys are homogeneous mixtures of metals. They cannot be separated into their individual components by physical methods. An alloy shows the properties of its constituents and can have variable composition. For example, brass is a mixture of 30% zinc and 70% copper.

Components of a Solution

Substances that make up a homogeneous solution are called components of the solution and they are solvents and solutes.

• Solvent: The component of a solution which dissolves the other component in itself is called solvent. A solvent constitutes the larger component of the solution. For example, a solution of sugar in water is solid in the liquid. Here, sugar is the solute and water is the solvent.

• Solute: The component of the solution which dissolves in the solvent is called solute. The solute is the smaller component of the solution. For example, in carbonated drinks (soda or pop), carbon dioxide gas is the solute.

Characteristics of Solutions

• It is a homogeneous mixture

• The size of solute particles in the solutions is extremely small. It is less than 1 nm in diameter.

• The particles of a solution cannot be seen even with a microscope.

• The particles of a solution pass through the filter paper. Thus filtration cannot separate the solution.

• It is very stable. The particles of solute present in a solution do not separate out on keeping.

• A true solution does not scatter light (because its particles are very small).

Concentration of a Solution

The concentration of a solution is the amount of solute present in a given quantity of it. In other words, the concentration of a solution is the mass of the solute in grams, which is present in 100 g of a solution. Depending upon the amount of solute present, it is called a dilute, concentrated or a saturated solution.

Different substances in a given solvent have different solubilities at the same temperature. The concentration of the solutions refers to the percentage of solute present in the solutions. Solubility is the amount of solute (in gram), which dissolves in 100 g of water (solvent), at a given temperature.

concentration = particles of solute / volume of solvent

Types of Solutions

• Saturated Solutions: Saturated solutions are solutions dissolving as much solute as it is capable of dissolving at a given temperature.

• Unsaturated Solutions: Unsaturated solutions are the ones with a lesser amount of solute than what we require for saturation. Sometimes, by applying external forces like heat energy, you can increase the solubility of the solutes in the solutions.

• Supersaturated Solutions: Supersaturated solutions contain more solute than saturated solutions.