A Diluted solution Or unsaturated Is a chemical solution that has not reached the maximum concentration of solute dissolved in a solvent. The additional solute will dissolve upon addition in a dilute solution and will not appear in the aqueous phase (Anne Marie Helmenstine, 2016).
From a physico-chemical point of view, an unsaturated solution is considered a state of dynamic equilibrium where the rates at which the solvent dissolves the solute are greater than the rate of recrystallization (J., 2014).
An example of a dilute solution is illustrated in Figure 1. In Figure 1.1, 1.2 and 1.3 there is a constant volume of water in the beaker.
In Figure 1.1 begins the process where the solute begins to dissolve, represented by the red arrows. In this case, two phases are seen, one liquid and one solid.
Figure 1: Example of unsaturated solution.
In Figure 1.2, much of the solid has dissolved, but not completely due to the recrystallization process, represented by the blue arrows.
In this case, the red arrows are larger than the blue arrows, which means that the rate of dilution is greater than that of recrystallization. At this point we have an unsaturated solution (tipes of saturation, 2014).
Thus, we can say that a diluted solution can dissolve more solute in it until it reaches the point of saturation. At the point of saturation, no more solute will dissolve in the solvent and such solution is called Saturated solution .
In this way the solutions are unsaturated in nature initially and eventually become solutions saturated by the addition of solute in it.
What is a diluted solution?
A diluted solution is that unsaturated, saturated or supersaturated solution to which more solvent is added. The result is an unsaturated solution with lower concentration.
Dilutions are a common process in a chemical laboratory. Generally, we work with diluted solutions that are made from mother solutions that are those that are acquired directly from a particular merchant.
To make the dilutions, use the formula C 1 V 1 = C 2 V 2 Where C is the concentration of the solution, generally in terms of molarity or normality. V is the volume of the solution in ml and the terms 1 and 2 correspond to the concentrated and diluted solutions respectively.
Factors Affecting Solubility
The amount of solute that can be dissolved in a solvent will depend on different factors, among them the most important are:
1- Temperature.
Solubility increases with temperature. For example, more salt can be dissolved in hot water than in cold water.
However, there may be exceptions, for example, the solubility of the gases in water decreases with increasing temperature.
In this case, the solute molecules receive Kinetic energy On heating which facilitates their escape.
2- Pressure.
The increase in pressure can force solute dissolution. This is commonly used to dissolve gases into liquids.
3- Chemical composition.
The nature of the solute and the solvent and the presence of other chemical compounds in the solution affect the solubility.
For example, a greater amount of sugar can be dissolved in water, than salt in water. In this case it is said that sugar is more soluble.
He ethanol And water are completely soluble with each other. In this particular case, the solvent will be the compound that is in the greatest amount.
4. Mechanical factors.
In contrast to the rate of dissolution, which depends mainly on temperature, the rate of recrystallization depends on the concentration of solute on the surface of the crystalline lattice, which is favored when a solution is immobile.
Hence, the agitation of the solution avoids this accumulation, maximizing dissolution (Tipes of saturation, 2014).
Saturation and solubility curves
Solubility curves are a graphical database where the amount of solute that dissolves in an amount of solvent at a given temperature is compared.
Solubility curves are commonly plotted for an amount of solute either solid or gas in 100 grams of water (Brian, 2014). Figure 2 illustrates saturation curves for various solutes in water.
Figure 2: saturation curves. In the abscissa, the degrees of temperature are represented, while in the ordinate, the grams of solute in 100 grams of water.
The curve indicates the saturation point at a given temperature. The area below the curve indicates that there is an unsaturated solution and therefore more solute can be added. In the area above the curve is a supersaturated solution (Solubility Curves, s.f.).
Taking sodium chloride (NaCl) as an example, about 35 grams of NaCl in 100 grams of water can be dissolved at 25 degrees centigrade to obtain a saturated solution (Cambrige University, s.f.).
Examples of diluted solutions
Unsaturated solutions can be found on a daily basis, it is not necessary to be in a chemical laboratory.
The solvent does not necessarily have to be water. The following are examples of everyday diluted solutions:
- Adding a tablespoon of sugar to a cup of hot coffee produces a solution of unsaturated sugar.
- Vinegar is a dilute solution of acetic acid in water.
- Fog is an unsaturated (but close to saturated) solution of water vapor in the air.
- 0.01 M HCl is an unsaturated solution of hydrochloric acid In water.
- Disinfecting alcohol is a diluted solution of isopropyl alcohol in water.
- The soup is an unsaturated solution of water and sodium chloride.
- Alcoholic beverages are dilute solutions of ethanol and water. Usually shows the percentage of alcohol they have.
References
- Anne Marie Helmenstine, P. (2016, July 7). Saturated Solution Definition and Examples . Retrieved from about.com.
- Cambridge University. (S.f.). Solubility curves . Retrieved from dynamicscience.com.au.
- Examples of Saturated Solution . (S.f.). Retrieved from examples.yourdcitionary.com.
- J., S. (2014, June 4). Saturated and Supersaturated Solutions . Retrieved from socratic.org.
- James, N. (s.f.). Saturated Solution: Definition & Examples . Retrieved from study.com.
- M., B. (2014, October 14). Saturated and Supersaturated Solutions . Retrieved from socratic.org.
- Solubility Curves . (S.f.). Retrieved from kentchemistry.com.
- Types of saturation . (2014, June 26). Retrieved from chem.libretexts.org.