Sodium is a metal element. It is located in the third cycle and the IA group in the periodic table. It is a representative of alkali metal elements. The preparation method in the laboratory is to mix an equal amount of hydrochloric acid with sodium hydroxide to form a sodium chloride solution. The solution is then distilled to obtain sodium chloride crystals.

It is soft in texture and can react with water to form sodium hydroxide(NaOH). It releases hydrogen and is chemically active. Sodium is widely distributed in the form of salt on land and in the sea.

Sodium is also one of the important components in human muscle tissue and nerve tissue.

Discover a brief history

After volts invented batteries in the early 19th century, chemists in various countries have used batteries to break down water successfully.

British chemist David is constantly working on experimental research using batteries to break down various substances. He hopes to use batteries to break down caustic potash into oxygen and an unknown “base” because chemists at the time thought that caustic was an oxide.

He first experimented with a saturated solution of caustic potash (potassium hydroxide), and the result was the same as that of electrolyzed water, only hydrogen and oxygen were obtained.

Later he changed the experimental method, electrolytically melting the caustic potash, and appeared a metallic luster-like mercury-like bead on the cathode. Some beads immediately burned and exploded, forming a bright flame, and some beads did not burn.

Only the surface is darkened and covered with a white film. He put the small metal particles into the water, and immediately came out with a flame, rushing on the surface of the water and making a tingling sound.

In this way, David discovered metal potassium in 1807, and a few days later he obtained sodium metal from electrolytic sodium carbonate.

David named potassium and sodium as Potassium and Sodium, respectively, because potassium is derived from potassium hydroxide (Potash) and sodium is obtained from sodium carbonate (Soda), which remains in English today.

sodium metal

The chemical symbols K and Na of potassium and sodium are derived from their Latin names Kalium and Natrium, respectively.

Physical properties

Sodium is a silver-white cubic structural metal. It is soft and light and can be cut with a knife. The density is smaller than water, 0.97g/cm3, melting point 97.81 °C, boiling point 882.9 °C.

The new section of silver-white luster, in air oxidation of a dark gray transition, having anti-corrosion properties. Sodium is a good conductor of heat and electricity and has good magnetic permeability.

Potassium-sodium alloy (liquid) is a nuclear reactor thermal conductivity agent. Sodium simple substance also has good ductility and low hardness. It can be dissolved in mercury and liquid ammonia and dissolved in liquid ammonia to form a blue solution. Hardens at -20 °C.

A total of 22 isotopes have been discovered, including sodium 18 to sodium 37, of which only sodium 23 is stable and all other isotopes are radioactive.

Chemical properties

The chemical nature of sodium is very active, normal temperature and heating.

And oxygen gas, respectively compounds, water and react violently when large explosion. Sodium can also be burned in carbon dioxide, reacting with low-alcohols to produce hydrogen, and liquid ammonia with weak ionization ability can also react.

4Na + O2 = 2Na2O (normal temperature)

2Na + O2 = Na2O(heating or ignition)

2Na + 2H2O = 2NaOH + H2 ↑

2Na + 2CO2 = Na2CO3 + CO

2Na + 2ROH = 2RONa + H2 ↑ (ROH stands for low alcohol)

2Na + 2NH3(L) = 2NaNH2 + H2 ↑ (“2NH 3(L) ” in this reaction means liquid ammonia)

The outermost layer of the sodium atom has only one electron, which is easily lost, so it has strong reducibility.

Therefore, the chemical properties of sodium are very active and can react with a large number of inorganic substances, most non-metal elemental reactions, and most organic substances.

When redox reaction with other substances occurs, the reducing agent is raised from 0 to +.

The 1 valence (due to the ns 1 electron pair) is usually combined in the form of an ionic bond and a covalent bond. Strong in metal and weak in ionic oxidation. The relative atomic mass of sodium is 22.989770.

High school chemistry believes that the sodium salt is soluble in water, but in fact, sodium uranyl zinc acetate, sodium uranyl acetate, sodium uranyl acetate, sodium citrate, sodium citrate, sodium titanate are insoluble in water.

Preparation

David Law

David is the first metal sodium produced by electrolysis. In the following decades, the industry uses iron powder and high-temperature sodium hydroxide to prepare sodium metal and simultaneously obtains ferroferric oxide and hydrogen.

Electrolytic sodium hydroxide also gives metallic sodium, but this method is less used. Currently, sodium chloride – calcium chloride molten salt electrolysis is commonly used in the industry to produce sodium metal.

Sfa

Calcium chloride is added to the molten salt of salt ( sodium chloride), heated in an oil bath and electrolyzed at a temperature of 500 °C and a voltage of 6 V.

Metal sodium is formed at the cathode by electrolysis, and chlorine gas is generated at the anode. It is then purified and packaged with liquid paraffin.

Chemical equation:

sodium bicarbonate

Casnafa

Using sodium hydroxide as raw material, it is placed in an iron container, the melting temperature is 320-330 °C, nickel is used as the anode, iron is used as the cathode, and a nickel mesh separator is placed between the electrodes.

The electrolysis voltage is 4 to 4.5 V, and the cathode is precipitated with sodium metal. And release oxygen. The prepared sodium metal is refined and packaged in liquid paraffin.

Chemical equation:

sodium bicarbonate

(In this experiment, since the density of sodium in the molten state is about 0.968 g/cm3, and the density of sodium hydroxide in the molten state is about 2.130 g/cm3, the finally produced sodium element in the molten state floats on The molten sodium hydroxide is dangerously combined with the oxygen in the air, so carry out this experiment under the protection of rare gases, otherwise it will be dangerous!)

Industrial applications

Determination of chlorine in organic matter. Reduction and hydrogenation of organic compounds. Test nitrogen, sulfur, and fluorine in organic matter. Remove moisture from organic solvents ( benzene, hydrocarbons, ethers ). Impurities such as oxygen, iodine or hydroiodic acid in the hydrocarbon are removed. Prepare sodium amalgam, sodium alkoxide, pure sodium hydroxide, sodium peroxide, sodium amide, alloy, sodium lamp, photocell to prepare active metal.

Physiological action

Sodium is an important inorganic element in the human body. Under normal circumstances, the sodium content in adults is about 3200 (female) ~ 4170 (male) mmol, about 0.15% of body weight, sodium in the body is mainly in extracellular fluid, accounting for total sodium. 44% to 50%, the content of bones accounts for 40% to 47%, and the intracellular fluid content is low, accounting for only 9% to 10%.

  1. Sodium is the main positive ion in the extracellular fluid, which participates in the metabolism of water, ensures the balance of water in the body, and regulates the body’s water and osmotic pressure.
  2. Maintain the balance of acid and alkaliin the body.
  3. It is a component of pancreatic juice, bile, sweat, and tears.
  4. Sodium has a relationship with the production and utilization of ATP (adenine nucleoside triphosphate), muscle movement, cardiovascular function, and energy metabolism. In addition, sodium metabolism is required for the utilization of sugar metabolism and oxygen.
  5. Maintain normal blood pressure.
  6. Enhance neuromuscular excitability.

The main source of human sodium is food. Sodium is absorbed in the upper part of the small intestine, and the absorption rate is extremely high, and almost all of it can be absorbed, so the amount of sodium in the feces is small.

The absorption of sodium in the jejunum is mostly passive, and in the ileum, it is mostly active absorption.

Sodium and calcium within the tubular reabsorption process occur competition, so that high sodium intake, the weight will be reduced calcium absorption, increased urinary calcium excretion.

Because the loss of urinary calcium is about 50% of calcium retention, high sodium diet has a great impact on calcium loss.

People who are exposed to high temperatures, heavy physical labor, and frequent sweating need to pay attention to sodium supplementation (drinking light saltwater, etc.).

Sodium is ubiquitous in various foods. Generally, animal foods are higher than plant foods, but the source of human sodium is mainly salt, and sodium or sodium-containing complexes (such as glutamic acid, small) added during processing and preparation of food. Soda, etc., as well as soy sauce, salted or cured meat or smoked food, pickles, fermented soy products, salty snack foods, etc.

In the human body, sodium is not easy to be lacking under normal circumstances, but in some cases, such as fasting, eating less, when the dietary sodium is too restrictive and the intake is very low, or at high temperature, heavy physical labor, excessive sweating, gastrointestinal diseases, Repeated vomiting, diarrhea, excessive sodium excretion, and loss, or certain diseases, such as Edison disease caused by the kidney can not effectively retain sodium, when parenteral nutrition is sodium or low sodium, the use of diuretics inhibits tubular reabsorption Sodium can cause sodium deficiency.

The lack of sodium is not obvious in the early stages, burnout, apathy, no god, and even fainted when standing up. When the sodium loss is 0.5g/kg or more, nausea, vomiting, blood pressure drop, painful Gil, and no chloride in the urine can be detected.

Under normal circumstances, too much sodium intake does not accumulate, but in some special cases, if salt is added to the baby milk powder, it can cause poisoning or even death.

Acute poisoning can lead to edema, increased blood pressure, elevated plasma cholesterol, decreased fat clearance, and damage to gastric mucosal epithelial cells. The appropriate in the taking of sodium (AI) is 2200 mg/d for adults.

Storage Method

It is immersed in liquid paraffin, mineral oil and benzene series and stored in a sealed form. A large amount is usually stored in an iron drum and sealed with argon gas.

Metal sodium cannot be stored in kerosene because it reacts with organic acids such as kerosene to form a substance such as sodium silicate (yellow) attached to the surface of sodium.

When stored in paraffin oil, the oxygen in the air also enters the paraffin oil, causing the surface of the metallic sodium to become gray to form an oxide film.

It can be soaked in kerosene when stored in small quantities with low purity requirements, such as laboratory storage.

Store in a cool, dry place away from fire and heat. Small amounts are generally stored in liquid paraffin.

It is distributed with oxidants, acids, and halogens.

Extinguishing: graphite powder, sodium carbonate dry powder, calcium carbonate dry powder. Disabling water and halogenated hydrocarbons to extinguish fires.

Sodium Chloride

Sodium chloride is an ionic compound, chemical formula NaCl, colorless cubic crystal or fine crystalline powder, tastes salty. The appearance is white crystal, the source of which is mainly seawater, which is the main component of salt.

Soluble in water, glycerin, slightly soluble in ethanol (alcohol), liquid ammonia, insoluble in concentrated hydrochloric acid. Impure sodium chloride is deliquescent in the air.

The stability is relatively good, the aqueous solution is neutral, and the industry generally uses electrolytic saturated sodium chloride solution to produce hydrogen, chlorine and caustic soda (sodium hydroxide) and other chemical products (generally called Chlor-alkali industry).

It can be used for ore smelting (electrolytic melting of sodium chloride crystals to produce active sodium metal), medically used to configure physiological saline, and can be used for condiments in life.

Sodium chloride is a white odorless crystalline powder. It has a melting point of 801 °C and a boiling point of 1465 °C. It is slightly soluble in ethanol, propanol, and butane.

It becomes a plasma after being miscible with butane and is easily soluble in water. The solubility in water is 35.9 g (room temperature).

NaCl is dispersed in alcohol to form a colloid, and its solubility in water is reduced by the presence of hydrogen chloride and is hardly soluble in concentrated hydrochloric acid.

It is odorless and salty and easy to deliquesce. Soluble in water, soluble in glycerin, almost insoluble in ether.

The crystals of sodium chloride form a stereo symmetry. In its crystal structure, the larger chloride ions are arranged in the closest packing, and the smaller sodium ions fill the octahedral gap between the chloride ions.

Each ion is surrounded by six other ions. This structure is also present in many other compounds, called sodium chloride or stone salt structures.

  • Electrolytic molten sodium chloride to prepare sodium metal

sodium bicarbonate

  • Electrolyzed brine

sodium

  • Reaction with silver nitrate

sodium

Ion equation:

sodium

(The essence is the nature of Cl )

  • Reaction with concentrated sulfuric acid (laboratory hydrogen chloride)

sodium chloride

(Growth stands for thick, excess stands for excess)

sodium chloride