Solutions: concentration, mass fraction. The definition, calculation and recommendations

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2018-03-25 03:22:19

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Mass concentration of the solution is one of the common concepts in modern chemistry. In the article we will identify the features of the solutions, their types, application. We will show several examples of calculation of different types of concentrations.

mass concentration

Solutions

A Solution is a homogeneous system having a variable composition. Two components of the solution, one always acts as environment. It will dissolve the structural fragments of other substances. It is called the solvent, within which are molecules of the solute.

If you mixed two gaseous substances, in this case, it does not emit solvent. For each specific situation always held special calculations.

Obtaining homogeneous systems

To obtain homogeneous solutions it is necessary the fragmentation of the solutes to the structural units. Only in this case the system will be true. At breaking up the small droplets, grains of sand, which will be distributed in the environment, get colloidal solutions, emulsions, suspensions.

concentration mass fraction

Application solutions

By the Way, in the construction of a mixture of sand, cement, water also called a solution, but from a chemical point of view it is a suspension. The practical importance of solutions can be explained for different reasons.

Chemical reactions in liquid solution occur in the bulk of the solvent. This makes them available for the reaction without any additional steps on the system. In the mixture containing solid particles, it is impossible to carry out the reaction in full. To speed up the process, you will need the contact of the particles at some points. To increase the speed of reaction of the ground crystals in a mortar, and then pressed them. But it is not immediately possible to achieve completeness of the process.

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The solution also is different. The molecules move freely, when collisions occur chemical transformations. The energy that begins to stand out in this interaction, the solvent is accumulated, the system is practically not heated.

mass concentration

Physical properties and concentrations of solutions

Mass fraction of substances allows to determine the proportion of the solute and solvent taken to make them. Metallic alloys, by the way, are also solutions, but a solid, characterized by certain physical parameters.

Solutions have the ability to change the force of the dissolved component. This makes them popular in agriculture, medicine. For example, a solution of potassium permanganate (potassium permanganate) is used for the treatment of abrasions and wounds in high concentration. But the practical importance is negligible concentration. So, the mass fraction of substances 2-3% makes the solution slightly pink color, popular for gastric lavage.

The Dark purple crystals of potassium permanganate not used for medical purposes, as they possess strong oxidizing properties. In General, the color intensity correlates directly what is its concentration. Mass fraction of substances allows you to adjust the toxicity of the final solution.

molar mass concentration

Mass fraction

How is this concentration? Mass fraction of substances is characterized by the ratio of the mass of a substance to the mass of the solution taken in percent. Their organoleptic properties are influenced not only something that will dissolve but also a quantitative indicator. For example, a weak solution of salt almost no distinctive flavor, and at high concentrations it is manifested in different degrees.

How, in practice, is determined by the concentration? Mass fraction of substances in solution is considered in the school course of inorganic chemistry. Tasks on the definition included in the tests for 9-form students.

Here is an example job that uses concentration.

Mass fraction of salt by 25%. The mass of the solution was 250 grams. Determine the mass of water contained in it. For calculations, first we need to find the mass of the substance. On the basis of proportions, we obtain that substance in a solution of 62.5 grams. To determine the mass of water be subtracted from 250 grams of the mass of the substance, the result is 187,5 g.

concentrations of solutions mass percentage

Types of concentrations

What is the concentration? Mass fraction in the solution may contain not more than one hundred percent. In chemistry, the term “focus” suggests that the content of dissolved substances. There are several options: molar, mass concentration.

For Example, if you want to prepare a solution of 80 grams of water and 20 grams of salt to determine the mass fraction of a substance in a solution, you first need to determine the mass of the solution. It will amount to one hundred grams. Covers percentage substance obtained 20 per cent.

We analyzed, which represents a mass fraction. The molar concentration assumes the ratio of the amount of a substance to the volume of the taken solution. To prepare a solution with a given molar concentration, first determine the mass of the substance. Then weigh it needthe amount and dissolve in a liter of solvent.

Calculation of molar concentration

So to make 2 liters of solution with a concentration of 0.15 mol/l first, calculate the mass of salt contained in the solution. To do this, divide 0,15 mole in 2 liters, get 0,075 mol. Now calculated mass: 0,075 mol multiply by 58.5 g/mol. The result is 4.39 g.

Objectives of analytical chemistry

As an application consider the task of chemical analysis. With its help reveal the composition of the mixture, conduct diagnostic tests, analyze rocks. You need to determine the qualitative and quantitative composition of the solution.

Among those tasks that are most often found in inorganic chemistry, highlight the determination of the concentration of one substance in a given amount of another substance. Through experiments, it is possible to implement a gradual adding to the solution, which has a known molar concentration of the desired solution. This process is called titration.

Solubility and solvents

The Most common solvent is water. It is perfectly soluble bases, acids, salts, some organic compounds. It aqueous solutions are the most common in nature systems. Water performs the function of a biological solvent. It is considered the basis for the occurrence of many mediums: blood, cytosolic, intercellular fluids. Many types of animals and plants live in the aquatic environment.

Solubility refers to the ability of a substance to dissolve in the selected solvent. It is a complex phenomenon, which requires taking into account certain nuances and peculiarities of solvent.

As a good organic matter can be noted alcohols. They are in your composition include gidroksilnye group, therefore have a high solubility.

mass fraction molar concentration

Conclusion

Any liquid can be regarded as solvent. That is why many are talking about the mutual solubility of the various liquid substances. For example, among the organic substances mention can be made of the water solubility of esters.

Different types of concentrations used in inorganic and organic chemistry, to help carry out qualitative and quantitative determination of substances. Theory of solutions in demand in analytical chemistry, pharmaceutical industry and modern medicine.


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Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."

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