Sodium chloride - sodium chloride is used as an additive to food, food preservative.It is also used in the chemical industry, medicine.It serves as an important raw material for production of caustic soda, hydrochloric acid, sodium and other substances.The formula of table salt - NaCl.
Education ionic bond between sodium and chlorine
chemical composition of sodium chloride reflects the conditional formula NaCl, which gives an idea of the equal number of atoms of sodium and chlorine.But the substance is not formed by diatomic molecules, and is made up of crystals.In the reaction of alkali metal with strong nonmetal each sodium atom gives valence electron more electronegative chlorine.There are sodium cations Na +, and the anions of the acid residue of hydrochloric acid Cl-.Oppositely charged particles are attracted to form a compound with an ionic crystal lattice.Little sodium cations located between the major anions of chlorine.The number of positive particles consisting of sodium chloride equal to the amount of negative substance is generally neutral.
chemical formula.Table salt and halite
salts - a complex structure of ionic substances whose names begin with the name of the acid moiety.The formula of table salt - NaCl.Geologists such mineral composition called "halite", and sediment - "rock salt".Old fashioned chemical term that is often used in the production - "sodium chloride".This substance is known to people since ancient times, when it was considered a "white gold".Modern students of schools and students in reading equations reactions involving chemical called sodium chloride marks ("sodium chlorine").
carry out simple calculations using the formula of substance:
1) Mr (NaCl) = Ar (Na) + Ar (Cl) = 22,99 + 35,45 = 58,44.
relative molecular weight of 58.44 (in amu).
2) is numerically equal to the molecular weight of the molar mass, but this value has a unit g / mol M (NaCl) = 58,44 g / mol.
3) The sample weight of 100 grams of salt contains 60.663 g of chlorine atoms and 39.337 g of sodium.
Physical properties of salt
fragile crystals of halite - colorless or white.In nature, there are also deposits of rock salt, painted in gray, yellow or blue.Sometimes mineral substance has a red tint, due to the kind and amount of impurities.Halite hardness on the Mohs scale is only 2-2.5 glass leaves on the surface of the line.
other physical parameters of sodium chloride:
- smell - is absent;
- tastes - salty;
- Density - 2.165 g / cm3 (20 ° C);
- melting temperature - 801 ° C;
- boiling point - 1413 ° C;
- solubility in water - 359 g / l (25 ° C);
Preparation of sodium chloride in the laboratory
By reacting sodium metal with chlorine gas in the tube is formed white substance - sodium chloride NaCl (Formula salt).
Chemistry provides insight into the different ways of getting the same connection.Here are some examples:
neutralization: NaOH (aq.) + HCl = NaCl + H2O.
redox reaction between the metal and acid:
2Na + 2HCl = 2NaCl + H2.
acids on metal oxide: Na2O + 2HCl (aq.) = 2NaCl + H2O
Displacement of a weak acid from a solution of its salt stronger:
Na2CO3 + 2HCl (aq.) = 2NaCl + H2O + CO2 (gas).
For use in an industrial scale all of these methods are too expensive and complex.
production of salt
Even at the dawn of civilization, people knew that after salting meat and fish stored longer.Transparent, the correct form halite crystals were used in some ancient countries instead of money, and were at a premium.Search and development of deposits of halite allowed to meet the growing needs of the population and industry.The most important natural sources of salt:
- halite mineral deposits in various countries;
- water of the seas, oceans and salt lakes;
- layer and crust of rock salt on the shores of salt water;
- halite crystals on the walls of volcanic craters;
- salt marshes.
In the industry there are four basic ways to produce salt:
- leaching of halite from underground layers, resulting evaporation of the brine;
- mining in salt mines;
- evaporation of sea water or brine of salt lakes (77% by weight of dry residue accounts for sodium chloride);
- use a byproduct of desalination of saline water.
chemical properties of sodium chloride
The composition of NaCl - is the average salt formed with alkali and acid soluble.Sodium chloride - a strong electrolyte.The attraction between the ions is so great that it can only destroy the highly polar solvents.In water the ionic crystal lattice substance decomposes exempt cations and anions (Na +, Cl-).Their presence is due to the electrical conductivity, which has a salt solution.The formula in this case is written as well as for solids - NaCl.One qualitative reactions to sodium cation - yellowing burner.To get the result you need to gain experience on the net wire loop a little solid salt and add to the middle of the flame.Properties salt also is a feature of the anion, which consists in the qualitative response to chloride ion.When interacting with silver nitrate in the solution a white precipitate of silver chloride (photo).Hydrogen chloride salt is displaced from a stronger acid than hydrochloric: 2NaCl + H2SO4 = Na2SO4 + 2HCl.Under ordinary conditions of sodium chloride does not undergo hydrolysis.
Applications rock salt
Sodium chloride lowers the melting point of ice, so in the winter on the roads and sidewalks using a mixture of salt and sand.It absorbs a large amount of impurities during the melting pollute rivers and streams.Road salt also accelerates the corrosion of car bodies, damaging trees planted near the road.In the chemical industry, sodium chloride is used as a raw material for a large group of chemicals:
- hydrochloric acid;
- metallic sodium;
- chlorine gas;
- caustic soda and other compounds.
In addition, salt is used in the manufacture of soap, dyes.As a food preservative used in canning, pickling mushrooms, fish and vegetables.To combat disorders of the thyroid gland in the formula of the population of table salt is enriched by the addition of safe iodine compounds, for example, KIO3, KI, NaI.These additives support the production of thyroid hormone, prevent disease endemic goiter.
value of sodium chloride to the human body
Formula sodium salt, its composition has acquired vital importance to human health.Sodium ions are involved in the transmission of nerve impulses.The anions of chlorine needed to produce hydrochloric acid in the stomach.But too much of salt in the diet can lead to high blood pressure and increased risk of heart disease and blood vessels.The medicine for high blood loss in patients administered with physiological saline solution.To obtain it in one liter of distilled water was dissolved 9 g of sodium chloride.The human body needs a continuous supply of this substance in food.Displayed salt through the excretory organs and skin.The average content of sodium chloride in the human body is about 200 g per day Europeans consume about 2-6 grams of sodium chloride, in hot countries the figure above in connection with higher perspiration.
