Soda Ash

What is Soda Ash?

Soda Ash is the common name for sodium carbonate, which is a chemical compound with the formula Na₂CO₃. This compound is also known as washing soda and soda crystals. Soda ash can be categorised as an inorganic compound. It can be noted that all hydrates of sodium carbonate are referred to as soda ash. It can also be noted that all these forms of sodium carbonate are white solids under standard conditions. Soda ash is water-soluble and is known to form slightly alkaline solutions when dissolved in water. Traditional methods of obtaining soda ash involved the burning of plants that grow in sodium-rich soils and collecting their ashes (hence the name).

Sodium carbonate is known to be a diazonium salt of carbonic acid (a chemical compound with the formula H₂CO₃). When dissolved in water, soda ash is known to form carbonic acid and sodium hydroxide. In its pure form, soda ash exists as a white powder and is known to be odourless. It can also be noted that soda ash is a relatively strong base that can act as an antacid.

The preparation of soda ash is generally done using one of four processes – the Leblanc process, the Dual-process, the Solvay process, and the Electrolytic process. Soda ash is a weak acid that is slightly soluble in ethanol and insoluble in alcohol. One of the important applications of this compound is as a water softener.

Preparation of Soda Ash

Soda ash is typically prepared with the help of the Solvay process. In the Solvay process, ammonia and carbon dioxide are passed into a saturated solution of sodium chloride (kept at a relatively low temperature). This triggers certain chemical reactions, resulting in the formation of sodium hydrogen carbonate. This compound is only very slightly soluble in the presence of sodium ions (as a consequence of the common-ion effect). Therefore, the sodium hydrogen carbonate is almost completely precipitated. It is then removed via the process of filtration and subsequently ignited in order to produce soda ash.

Structure of Soda Ash

The structure of soda ash (sodium carbonate) molecules is illustrated in the image provided below. It is important to note that each molecule of sodium carbonate contains 3 oxygen atoms, 2 sodium atoms, and one carbon atom. Each sodium cation is known to hold a charge of +1. On the other hand, the polyatomic carbonate anion is known to hold a net charge of magnitude -2. Therefore, soda ash is a neutrally charged molecule.

Properties of Soda Ash

• The chemical formula of soda ash is Na₂CO₃.
• The molar mass of anhydrous soda ash is roughly equal to 106 grams per mole. The decahydrate of this compound is known to have a molar mass of 286.14 grams per mole.
• Under standard conditions for temperature and pressure (often abbreviated to STP), soda ash is known to exist as a white solid that is hygroscopic in nature. It can be noted that this compound does not have any characteristic odour.
• At a temperature of 25 degrees Celsius, soda ash is known to have a density of 2.54 grams per cubic centimetre (in its anhydrous state).
• Anhydrous soda ash is known to have a melting point corresponding to 851 degrees Celsius.
• Soda ash is quite soluble in water. At a temperature of 100 degrees Celsius, the solubility of anhydrous soda ash in water is roughly equal to 436 grams per litre.

Applications of Soda Ash

Soda ash is widely used as a cleaning agent for several domestic purposes such as the washing of clothes. It is also known to be an important component of several dry soap powders.

Soda ash functions as a silica flux, working to reduce the melting point of the mixture without any need for special materials. The resulting “soda glass” is slightly water-soluble, so the melt mixture is added with some calcium carbonate to make the glass insoluble. The melting of such blends of sodium carbonate, calcium carbonate, and silica sand (also known as silicon dioxide) creates bottle and window glass (soda-lime glass).

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