Acids-Bases and Salts / Preparation Important Compounds

Acid-bases and salts

* Preparation and uses of important compounds.

I) Caustic Soda (Sodium Hydroxide, NaOH)

Preparation of Sodium hydroxide

Preparation: In the process of electrolytic decomposition of brine (aqueous solution of sodium chloride), brine decomposes to form sodium hydroxide.

2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g)

In this process, chlorine is moved towards anode and hydrogen gas is moved towards cathode as by products. This whole process is known as Chlor – Alkali process.

Uses:

Sodium hydroxide is used for degreasing of metals, manufacturing of paper, soap, detergents, artificial fibres, etc.

II) Bleaching Powder (Calcium Oxychloride, CaOCl2)

Preparation of Bleaching powder

Preparation: Bleaching powder is produced by the action of chlorine on dry slaked lime [Ca(OH)2].

Ca(OH)2 + Cl2→ CaOCl2 + H2O

Uses:

(i) It is use for bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry;

(ii) as an oxidising agent in many chemical industries; and

(iii) to make drinking water free from germs

III)Baking Soda (Sodium Hydrogen Carbonate, NaHCO3

Preparation of Baking soda

Preparation:

The chemical name of the compound is sodium hydrogen carbonate (NaHCO3). It is produced by the reaction of brine with carbon dioxide and ammonia. This is known as Solvay process.

NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3                                                                         

*Uses:

(i) Baking soda is used in making of baking powder, which is used in cooking.

Baking powder is a mixture of baking soda (sodium hydrogen carbonate) and a mild edible acid such as tartaric acid. When baking powder is heated or mixed in water, the following reaction takes place 

NaHCO3 + H+--------->CO2 + H2O + Sodium salt of acid

Carbon dioxide produced during the reaction can cause bread or cake to rise making them soft and spongy.

(ii) Baking soda (sodium hydrogen carbonate) is also an ingredient in antacids. Being alkaline, it neutralises excess acid in the stomach and provides relief.

(iii) It is also used in soda-acid fire extinguishers.

IV) Washing Soda (Sodium Carbonate, Na2CO3.10H2O )

Washing soda

*Preparation:

-> Sodium carbonate is manufactured by the thermal decomposition of sodium hydrogen carbonate obtained by Solvay process.

-> NaCl + NH3 + H2O + CO2 ------> NaHCO3 + NH4Cl

->NaHCO3 -------->Na2CO3 + CO2 + H2O

                Hea

  ->   Na2CO3 + 10 H2O → Na2CO3.10H2O

* Uses:

(i) Sodium carbonate (washing soda) is used in glass, soap and paper industries.

(ii) It is used in the manufacture of sodium compounds such as borax.

(iii) Sodium carbonate can be used as a cleaning agent for domestic purposes.

(iv) It is used for removing permanent hardness of water

Plaster of Paris (Calcium Sulphate Hemihydrate, CaSO4. ½ H2O)

* Preparation: POP-Gypsum:-

Gypsum

On heating gypsum at 373 K, it loses water molecules and becomes calcium sulphate hemihydrate(CaSO4. ½H2O) which is called Plaster  of Paris is a white powder and on mixing with water, it changes to gypsum once again giving a hard solid mass.

->CaSO4. ½H2O + 1½H2O ------>CaSO4.2H2O

Question for you 😊

-->What is that substance use by doctors to join broken bones ?

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Author:- Sachin Joshi