Sodium carbonate (Na2CO3) is a very important chemical in many industries and domestic purposes in the world. Due to weak basic characteristics and other specific chemical properties, Sodium carbonate shows variety of reactions. In this tutorial, we will see how Sodium carbonate reacts with other chemicals.
Sodium carbonate is introduced in many names such as washing soda or soda ash. It's is a water soluble and gives a colourless aqueous solution. Dissolved sodium carbonate completely dissolve to Sodium cation and carbonate ions in water as mentioned below.
Sodium carbonate is used to identify cations in qualitative analysis. It precipitates insoluble carbonates of calcium, barium and strontium and many more cations.
Carbonate ion gives insoluble metal carbonates with most of the metal cations. From metal carbonates, Sodium carbonate, Potassium carbonate, Rubidium carbonate, Cesium are soluble in water and other all carbonate compounds are insoluble in water.
When dilute acid (HCl, H2SO4) is added to a solid sodium carbonate (Na2CO3) , carbon dioxide gas is generated.
Sodium carbonate and carboxylic acids (RCOOH) react to give Carbon dioxide (CO2) and sodium salt of carboxylic acid (RCOO-Na+) and water. Also sodium bicarbonate reacts with carboxylic acid to give CO2.
Note : Alcohols and phenol do not react with sodium carbonate and sodium bicarbonate to release carbon dioxide gas. This experiments is used to identify carboxylic acid from alcohols and phenols.
With hot milk of lime (Ca(OH)2), sodium carbonate react to form sodium hydroxide and calcium carbonate. Calcium carbonate exist as a precipitate.
All carbonates of alkali metals ( Group 1A) are stable to heat. Therefore decomposition of Na2CO3 is difficult.
There are two types of hardness of water as temporary hardness and permanent hardness. Na2CO3 can be used to remove both temporary hardness and permanent hardness.
Bicarbonate ion (HCO3-) of Ca2+ and Mg2+ ions cause to temporary hardness of water. Adding Sodium carbonate to hard water will form Calcium carbonate (CaCO3) and Magnesium carbonate (MgCO3) precipitates by replacing HCO3- anions.
Sulfate ions (SO42-) and Chloride ions (Cl-) of Ca2+ and Mg2+ cause to permanent hardness of water. Adding Sodium carbonate will form Calcium carbonate (CaCO3) and Magnesium carbonate (MgCO3) precipitates by removing Ca2+ and Mg2+ from water.
sodium carbonate is a basic compound. sodium carbonate dissociates completely in the water to Na+ ion CO32- ion. Na+ ion is stable in the water. But CO32- is not stable in the water and is hydrolyzed in the water.
By the hydrolysis of carbonate ion, OH- ions are released.
Due to release of OH-, sodium carbonate solution is weak basic.
Sodium carbonate is a white crystalline solid which exists as a decahydrate (Na2CO3.10H2O). This is called washing soda. When decahydrate gets heat, it looses the water of crystallization to form monohydrate ( Na2CO3.H2O). Above 373K, the monohydrate becomes completely anhydrous and changes to a white powder called soda ash.
With addition of calcium chloride (CaCl2), there are Na+, CO32-, Ca2+ and Cl- ions in the water. We know CaCO3 is a precipitate. Therefore in higher concentrations of Ca2+ and CO32- ions in aqueous solution, a white precipitate (CaCO3) is formed.