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CHEMISTRY FORM 2


1. STRUCTURE OF THE ATOM, AND THE PERIODIC TABLE
2. CHEMICAL FAMILIES AND PATTERNS IN PROPERTIES
3. CHEMICAL BONDING AND STRUCTURE
4. SALTS
5. EFFECT OF AN ELECTRIC CURRENT ON SUBSTANCES
6. CARBON AND SOME OF ITS COMPOUNDS
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Carbon and some of its compounds: Large scale production of sodium carbonate and sodium hydrogencarbonate

6.0 Carbon and some of its compounds


6.5 Large scale production of sodium carbonate and sodium hydrogencarbonate


These salts can either be manufactured or obtained from the natural source, trona. But the latter is much cheaper and therefore used where trona is available. In Kenya, trona is mined at Lake Magadi. Trona is a salt with the chemical formula Na2CO3.NaHCO3.2H2O


Questions 6.5

  1. What does the part, 2H2O, indicate to us about the salt?

  2. How many salts are represented in the formula of trona?

  3. From your knowledge of effect of heat on salts, describe the expected change when trona is heated till no further change occurs.

  4. Name the final product left.



Answers to Questions 6.5


Trona is a hydrated salt, consisting of two salts. It is a double salt. If we want sodium carbonate (Na2CO3) only, trona is heated strongly to remove water of crystallization, then decompose sodium hydrogencarbonate to sodium carbonate. Carbon (IV) oxide and more steam are released.


2Na2CO3.NaHCO3.2H2O(s)   ⟶   3Na2CO3(s)  +   3H2O(g)  +  CO2(g)


If both salts are required, they can be separated by fractional crystallization.


These salts have many uses in industries. For example, sodium carbonate is used to manufacture glass and water softeners. Sodium hydrogencarbonate is used as baking powder and in fire extinguishers to produce carbon (IV) oxide.