What is a chemical solution?

We explain what a chemical solution is and its main characteristics. In addition, how it is classified and what is the concentration.

  1. What is a chemical solution?

A homogeneous mixture of two or more substances whose bonding occurs to a degree such that their individual properties are modified or lost is called a chemical solution or solution . Thus, the union of both substances throws a new substance , with its own characteristics, in which the two mixed components are indistinguishable from each other.

In this way, the solution resulting from the mixture of the two components will have a single recognizable phase ( solid , liquid or gas ) even though its components have different phases. For example, dissolve sugar in water.

Every chemical solution has at least two components: one that is dissolved in the other and that we will call solute, and another that dissolves the solute and that we will call solvent or solvent. In the case of sugar water , the first will be the solvent and the second will be the solute.

The ability to form solutions and to mix substances is fundamental for the development of new materials and for the understanding of the chemical forces that allow matter to come together. This is of particular interest for the fields of chemistry , biology and geochemistry, among others.

  1. Characteristics of a chemical solution

Chemical solution
In a chemical solution its elements cannot be distinguished with the naked eye.

In general, every chemical solution is characterized by:

  • Soluto and solvent cannot be separated by physical methods such as decantation, filtration or sieving, since their particles have built new chemical bonds.
  • They have a solute and a solvent (at least) in some detectable proportion.
  • At first glance its constituent elements cannot be distinguished.
  • Only solute and solvent can be separated by methods such as distillation , crystallization or chromatography.
  1. Types of chemical solution

Chemical solutions can be classified according to the proportion that exists between solute and solvent, called concentration. There are, thus, four types of solutions:

  • Diluted . When the amount of solute with respect to the solvent is very small. For example: 1 gram of sugar in 100 grams of water.
  • Concentrated . When the amount of solute with respect to the solvent is large. For example: 25 grams of sugar in 100 grams of water.
  • Saturated . When the solvent no longer accepts more solute at a certain temperature, since its particles no longer have how to generate more bonds, it is said to be saturated. For example: 36 grams of sugar in 100 grams of water at 20 ° C.
  • Supersaturated . We will have noticed that saturation has to do with temperature: that is because by increasing the latter, the solvent can be forced to drink more solute than it can ordinarily, thus obtaining a supersaturated solution (excessively saturated, say). Thus, subjected to sudden heating or cooling, the solution will take much more solute than it could ordinarily.
  1. Concentration of a chemical solution

The concentration is a magnitude that describes the proportion of solute with respect to the solvent in a solution. This magnitude is expressed in two different types of units, which are:

Physical units . Those that are expressed in relation to the weight and volume of the solution, in percentage form (multiplied by 100). They can be the following:

  • % Weight / weight . It is expressed in grams of solute over grams of solution.
  • % Volume / volume .  It is expressed  in cc of solute over cc of solution.
  • % Weight / volume . Combine the previous two: gr of solute over cc of solution.  

Chemical units . Those that are expressed in chemical unit systems, such as:

  • Molarity (M) . It is expressed in number of moles of solute over one liter of solution or one kilogram of solution.
  • Molar fraction (Xi) . It is expressed in terms of moles of a component (solvent or solute) in relation to the total moles of the solution, as follows:

solution = moles of solute / moles of solute + moles of solvent 

sol vente = moles of solvent / moles of solute + moles of solvent 

Always contemplating that:

solvent solution  = 1  

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