- A salt is a compound formed from an acid by the replacement of the hydrogen in the acid by a metal.
- The salts of ‘hydrochloric acid’ are called ‘chlorides’.
- The salts of ‘sulphuric acid’ are called ‘sulphates’.
- The salts of ‘nitric acid’ are called ‘nitrates’.
- The salts of ‘carbonic acid’ are called ‘carbonates’.
- The salts of ‘acetic acid’ are called ‘acetates’, and so on.
- WATER OF CRYSTALLISATION :it refers to water molecules that are found in the crystalline structure of a metal complex or a salt, which is not directly bonded to the metal cation.
- HYDRATED SALTS -When crystalized salts contain water molecules as part of their structure, they’re known as hydrated salts.
- EXAMPLES –
- washing soda (sodium carbonate decahydrate, Na2CO3∙10H2O)
- Glauber’s salt (Na2SO4∙10H2O)
- borax (Na2B4O7∙10H2O)
- Epsom salt (MgSO4∙7H2O)
COMMON SALT (SODIUM CHLORIDE)
- The common salt is a white powder which is used in preparing food, especially vegetables and pulses, etc
- Common salt is also known as just ‘salt’. The chemical name of common salt is sodium chloride (NaCl).
- Common salt (or sodium chloride) is a neutral salt.
- Sodium chloride can be made in the laboratory by the combination of sodium hydroxide and hydrochloric acid :
- How common salt is obtained ?
- Common salt occurs in dissolved form in sea-water.
- On the other hand, common salt occurs in solid form as rock salt.
Uses of Common Salt
- it is an important raw material for various materials we use daily like
- sodium hydroxide, baking soda, washing soda, bleaching powder and many more.
- it is use in food.
- Used as a preservative in pickles and in curing meat and fish.
- Used in the manufacture of soap
- Sodium hydroxide is commonly known as caustic soda.
- The chemical formula of sodium hydroxide is NaOH.
- The process of electrolysis of sodium chloride solution is called chlor-alkali process
- chlor-alkali process– The chloralkali process is an industrial process for the electrolysis of sodium chloride solutions.
- It is the technology used to produce chlorine and sodium hydroxide.
- The three very useful products obtained by the electrolysis of sodium chloride solution called brine (or chlor-alkali process) are sodium hydroxide, chlorine and hydrogen.
Uses of Chlorine-
- it act as disinfectant to kill bacteria.
- It is used to treat drinking water and swimming pool water.
- it is used to produce paper, paints,textiles, insecticides and many more.
- 20% of chlorine produced is used to make PVC.
- It is used as an oxidising agent.
- Chlorine gas is itself very poisonous, and was used as a chemical weapon during the First World War.
Uses of HCL
- it help to digest your food in stomach.
- it is used in industry to make steel which is used to make
- suspension bridges and cars and trucks.
- it is used in the production of batteries, photoflash bulbs and fireworks.
- it is used to process sugar and make gelatin.
Uses Of Hydrogen
- use of hydrogen is to remove the sulfur that is naturally contained in oil to produce cleaner fuels.
- it is used as a reagent in many industrial sectors like chemicals,
- textile fiber manufacturing, glass, electronics and metallurgy.
- it is also used as fuel for rocket launchers.
- Hydrogen is used to produce clean and silent energy.
- Hydrogen used in a fuel cell allows us to produce electricity directly
- Washing soda is sodium carbonate containing 10 molecule of water of crystallisation.
- That is, washing soda is sodium carbonate decahydrate.
- The formula of washing soda is Na2CO3.10H2O.
- A cold and concentrated solution of sodium chloride (called brine) is reacted with ammonia and carbon dioxide to obtain sodium hydrogencarbonate
- On heating, sodium hydrogencarbonate decomposes to form sodium carbonate :
- The anhydrous sodium carbonate obtained here is called soda ash.
- Anhydrous sodium carbonate (soda ash) is dissolved in water and recrystallised to get washing soda crystals containing 10 molecules of water of crystallisation :
Uses of Sodium Carbonate (or Washing Soda)
- Sodium carbonate (or washing soda) is used as a “cleansing agent” for domestic purposes like washing clothes
- Sodium carbonate is used for removing permanent hardness of water.
- Sodium carbonate is used in the manufacture of glass, soap and paper.
- Sodium carbonate is used in the manufacture of sodium compounds such as borax.
PLASTER OF PARIS
- chemical formula of plaster of paris is (CaSO4)2. H2O
- On heating gypsum at 373 K, it loses water molecules and becomes
calcium sulphate hemihydrate .
- it is used by doctors as plaster for supporting fractured bones in the right position.
- Plaster of Paris is a white powder and on mixing with water, it changes to gypsum once again giving a hard solid mass.
- half a water molecule is to be attached as water of crystallisation in it.
USES OF PLASTER OF PARIS
- Plaster of Paris is used for making toys, materials for decoration
and for making surfaces smooth
- It is also used in medicine to make plaster casts to immobilize broken bones while they heal
- It is used for plastering fractured bones and holding them on fixed positions
- it is widely used by dentists
- chlorine gas is used for the manufacture of bleaching powder.
- Bleaching powder is produced by the action of chlorine on dry slaked lime [Ca(OH)2].
- Bleaching powder is represented as CaOCl2.
USES OF BLEACHING POWDER
- it is used for bleaching cotton and linen in the textile industry, for bleaching
wood pulp in paper factories and for bleaching washed clothes
- it is used as an oxidising agent in many chemical industries
- it is used to make drinking water free from germs