Supersaturated Solution - Definition, Examples, Applications, FAQs

Two or more substances are homogeneously combined to form a solution. Those substances that get dissolved are referred to as solute and those substances in which solute is dissolved are solvents. For example, salt (solute) dissolved in water (solvent). The concentration of the solution is determined on the basis of the amount of solute dissolved in the solvent. Based on the amount of solute that is dissolved in the solvent, solutions can be further classified as saturated solutions, Unsaturated Solutions, and supersaturated solutions.

In the article, we cover the topic classification of supersaturated solution which is the sub-topic of chapter Solutions. it is important for board exams and JEE Mains Exam, NEET Exam, and other entrance exams.

What is a Supersaturated Solution?

A supersaturated solution definition in chemistry is a solution containing more than the maximum amount of solute that can dissolve in solvent at a particular given temperature. A supersaturated solution possesses an unstable state; it could be made stable by separating the excess amount of solute dissolved in the solvent.

Examples of Supersaturated solution

Examples of supersaturated solutions include carbonated water (i.e. soda water), honey or sugar syrup used in confectionery, etc.

An example of supersaturation is shown by sodium thiosulfate (Na₂S₂O₃). It can dissolve 50 g Na₂S₂O₃ per 100 g of H₂O at room temperature. Suppose, 70 g of Na₂S₂O₃ crystal is dissolved in 100 g hot H₂O and the solution is then cooled to room temperature. Then the additional 20 g of Na₂S₂O₃ usually does not get precipitated.

The solution thus obtained is supersaturated and it is unstable. The recrystallization in a supersaturated solution can be performed by the addition of a small crystal of solute which is called a seed crystal. This process is defined as seeding in chemistry.

The nucleation site is provided by the seed crystal on which the extra dissolved crystals can begin to grow. The supersaturated solution of Na₂S₂O₃ can be seeded by the addition of a Na₂S₂O₃ crystal, in which the excess salt suddenly crystallizes and heat is liberated. After the crystals are settled and the temperature has cooled back to room temperature (25°C), the solution found above the crystal is saturated and it contains 50 g Na₂S₂O₃. Recrystallization is a very fast process from a supersaturated solution.

Supersaturation in Phase Change (Supersaturation Crystallization and Condensation)

• In each system, the physical and chemical processes of the vapor melt or the solution phase occurs by the formation of three-dimensional nuclei of a new phase and take place only during the supersaturated medium.
• The nuclei’s production is associated with a change in the free energy of the system. In the case of a homogeneous system, the new phase of the nuclei is not produced as soon as the system becomes supersaturated though thermodynamically, such a situation becomes possible.
• The system is found to be in a metastable equilibrium state, and it can remain in the same state without attaining the least or minimum free energy corresponding to the equilibrium state.
• In other words, in such cases, the nucleation of a new phase sets in after a time period, where the value depends on factors such as the pressure and temperature of the system, the presence of chemical phases varies from the increasing supersaturation level, and nucleating phase facilitates the nucleation process of the new phase.
• However, there is always a level of supersaturation when the new phase is instantaneously nucleated. It is referred to as the new phase precipitates.
• Such a supersaturation level signifies the upper limit of the metastable equilibrium state and describes the metastable width.

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Applications of Supersaturated Solution

• Supersaturation have practical applications in the field of pharmaceuticals. By preparing a supersaturated solution of a particular drug, it can be ingested in liquid form. The precipitation can be prevented by adding precipitation inhibitors. Drugs in such states are termed "supersaturating drug delivery services," or "SDDS." Oral consumption of a drug in this form is easy and helps in the measurement of very precise dosages.
• Marine ecologists use supersaturated solutions’ identification as a tool for the study of the activity of organisms and populations.
• Supersaturation is an important factor in the design of steam turbines.
• The study of supersaturation is also important for atmospheric studies. Actually, supersaturation of water is very common in the upper troposphere. This can be found using satellite data from the Atmospheric Infrared Sounder.

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