Sodium Chloride and Sodium Hydroxide - Practice Questions & MCQ

Sodium Chloride(NaCl)
It is called common salt or rock salt or sea salt or table salt. Seawater has nearly 2.95% NaCl. 28% aqueous NaCl solution is called brine.

Preparation
It is mainly manufactured from seawater by evaporation in the sun. As it contains impurities of MgCl₂, CaCl₂, CaSO₄ hence it is further purified by passing HCl gas where due to common ion effect pure NaCl gets precipitated.

Physical Properties

• It is a white crystalline solid and hygroscopic in nature.
• It melts at 1081K and boils at 1713K.
• It dissolves in water and the process of dissolution is endothermic.
• Its solubility is 36g per 100g of water at 273K. The solubility does not increase much with the increase in temperature.

Uses

• It is an essential constituent of our food.
• Ir is used in the manufacture of sodium, sodium hydroxide, washing soda, hydrogen chloride, chlorine, etc.
• It is used in freezing mixture.
• It is used for the preparation of soap.
• It is used for regenerating ion exchange resins.

Sodium Hydroxide(NaOH)
It is also known as caustic soda.

Preparation
Ir is prepared by the following methods:

• Gossage or Causticization Method
  In this method, a suspension of lime [CaO+Ca(OH)₂] is treated with sodium carbonate to obtain NaOH as follows:
  
• Lowig's Method
  Here a mixture of sodium carbonate and ferric oxide is heated in a revolving furnace up to redness to get sodium ferrite which is first of all cooled and hydrolyzed by hot water into NaOH solution and insoluble ferric oxide. The solution is filtered and evaporated up to dryness to get the flacks of NaOH.
  
  

Physical Properties

• It is a white crystalline, deliquescent soapy solid with a meting point of 591.4K.
• It is highly soluble in water bur less soluble in alcohol.
• It is corrosive in nature and bitter in taste.

Uses

• The manufacture of soap, paper, artificial silk and a number of chemicals.
• In petroleum refining.
• In the purification of bauxite.
• In the textile industries for mercerising cotton fabrics.
• For the preparation of pure fats and oils,
• As a laboratory reagent.