|
Unlimited Tutoring & Homework Help
|
|
General Preparation of Salts
Salts are generally ionic compounds formed by the reaction of an acid with a base. The preparation of these salts involves the treating of different metals and non-metals and their compounds with various acids, bases etc. However, some of them can be prepared by direct combination of the concerned elements or also by indirect routes.
Preparation of Certain Salts in the Laboratory
Preparing Zinc Sulphate
Take zinc granules in a beaker and dissolve them in dilute sulphuric acid. The zinc granules must be in excess. Effervescence of hydrogen gas appears immediately. Wait till the effervescence is over.
Preparation of Sodium Bicarbonate
Pass carbon dioxide through a solution of sodium carbonate for some time. Evaporate the resulting solution to dryness whereby sodium bicarbonate crystals separate out.
Preparation of Potassium Bicarbonate
Pass carbon dioxide through a solution of potassium carbonate for some time. Evaporate the resulting solution to dryness when potassium bicarbonate crystals separate out.
Water of crystallization
Water of crystallisation is a definite molecular proportion of water molecules, chemically combined to a salt in the crystalline state. This water of crystallisation is responsible for the geometric shape and colour of the crystals i.e., for the crystalline appearance of a salt.
Summary
Efflorescent substances are those, which lose water of crystallization to the atmosphere and crumble into powder.
