Many tasks in chemistry are associated with the calculation of the molar mass of the substance with which experiments are carried out. In the article, we consider one example of such problems and find what the molar mass of barium sulfate is equal to. We also consider in which areas of human activity this substance is used.
What is barium sulfate?
Before considering the molar mass of barium sulfate, we will take a closer look at this substance. From a chemical point of view, it is a salt formed by the sulfate anion and barium cation. Its formula can be written as follows: BaSO 4 .
Barium sulfate is a white powder that has a high chemical inertness. So, it not only does not dissolve in water, but also does not react with many alkalis and acids. It dissolves only in concentrated sulfuric acid, and is also reduced to barium oxide when heated above 1600 o C.
In nature, barium sulfate is found in many ores of this metal, for example, it is the main substance of the barite mineral.
Due to its white color and chemical inertness, this salt is used as a special “porridge” that the patient eats during the X-ray examination of the stomach (heavy barium atoms absorb X-rays well), and is also used in the manufacture of white dyes in plastics.
It is interesting to note that almost all barium salts are poisonous and, when ingested, cause severe poisoning. Barium sulfate in this regard is harmless due to its insolubility in the acidic environment of our stomach.
The concept of molar mass
Before answering the question of what is the molar mass of barium sulfate, it is necessary to understand this concept. Molar mass is the ratio of the mass of a substance to the number of moles of this substance, i.e. the mass of one mole of a substance
The word "mole" is one of seven basic or basic units of measure in the SI system, which was added to it in 1971. This value means the number of elements that make up the material in question. It can be atoms, molecules, ions, electrons, in the general case, any particles into which an object can be divided. The value of 1 mol is considered to be equal to the Avogadro number (N A = 6.022 * 10 23 ). Where did this number come from? It's simple, it exactly corresponds to the number of atoms in 2 grams of hydrogen gas (H 2 ), that is, 1 gram of atomic hydrogen (H) will also contain 1 mol of particles.
The use of this unit in physics and chemistry is convenient, due to the small size of atoms and molecules and their large number.
How to calculate the molar mass of barium sulfate?
Now that the concept of molar mass has been analyzed, we can proceed directly to the topic of the article. As can be understood from the previous paragraph, in order to calculate the mass of 1 mol of the salt in question, it is necessary to know how much one molecule weighs, i.e. BaSO 4 .
According to the chemical formula, the molecule in question consists of one barium atom, one sulfur atom and four oxygen atoms. The idea of ​​calculating its mass is to sum the atomic masses of the corresponding elements. The necessary data can be found in the periodic system of D. I. Mendeleev.
Using the periodic table: atomic molar masses
If we turn to the periodic system of chemical elements, we can see that in each cell representing a chemical element, information is given about the charge of the nucleus of its atom (serial number), the configuration of the outer electron shells, and also a certain number that reflects the molar mass of atoms of the corresponding element .
From the table we obtain the necessary molar masses:
- M (Ba): 137.327;
- M (S): 32.065;
- M (O): 15,999.
All given values ​​have the dimension of gram per mole (g / mol). Note that these numbers are the average value between the masses of different isotopes of one chemical element, the nuclei of which contain a constant number of protons, but the number of neutrons can vary. So, barium is actually a mixture of 6 isotopes that can be considered relatively stable because they have large half-lives.
The values ​​obtained from the periodic table for individual atoms can be used to determine what the molar mass of barium sulfate is.
Molar mass of BaSO4
In order to calculate the molar mass of barium sulfate 2 (the number indicates the valency that the metal atom exhibits in the chemical compound), it is necessary to add the corresponding values ​​for each element, taking into account their number in the salt molecule under consideration. Thus, the BaSO 4 compound is formed by 6 atoms: one atom of Ba and S and 4 O atoms. The molar mass of the compound is: M (BaSO 4 ) = 1 * M (Ba) + 1 * M (S) + 4 * M (O) = 1 * 137.327 + 1 * 32.065 + 4 * 15.999 = 233.388 g / mol.
In fairness, it should be noted that the formation of stable chemical compounds from individual atoms is accompanied by the release of a certain amount of energy. According to Einstein's equation (E = m * c 2 ), energy loss is equivalent to mass loss. Therefore, in reality, the molar mass of BaSO 4 will have a lower value than the calculated value, however, this correction is so insignificant that it is neglected.
The method for calculating the molar mass, considered using barium sulfate as an example, can be applied to absolutely any compound. For this, it is only important to know their chemical formulas.