NCERT SCIENCE ACID BASE AND SALT

 Acid are sour in taste and change the colour of blue litmus to red, Whereas bases taste bitter and change the colour of red litmus to blue.

Litmus is a natural indicator obtained from lichens.

Methyl orange and phenolphthalein are synthetic indicators.

A few reactive metals like zinc react with strong bases like NaOH to yield H2 gas.

Acids and bases react with each other to from salts and water, the process is called neutralisation.

The non-metal oxides like Co2, which is acidic react with bases to from salts and water.

The acids ionise in water and conduct electricity.

The pH of a solution (acid or base) is an indication of the strength of an acid or a base.

The pH of a neutral solution is 7. The pH less then 7 means acidic and more than 7 means basic.

The strength of acids and bases depends on the number of H+ ions and OH - ions produced.

NaOH is manufactured from common salt by chlor-alkali process.

Washing soda and baking soda are manufactured by. Solvay process from sodium chloride.

The colour of large number of salts is due to presence of water of crystallisation.

Plaster of Paris is obtained by heating of gypsum  (CaSO4, 2H2O) is chemically calcium sulphate hemihydrate.

                                         SOME MORE DEFINATION  

   

Acids: Those substances which give H+ ions in aqueous solution are called acids.They are sour in taste and trun blue litmus red.

Bases:  Those substances which give OH- ions in aqueous solution are called bases. They are bitter in taste and turn red litmus blue.

Salts:  when an acid reacts with a base or a metal then the compounds formed are called salts.

Alkalies: Those bases which are soluble in water are called alkalies.

Indicators: Those substances which change there colour in acidic or basic media are called (acid-base) indicators.

Antacids:  Those substances which are used to neutralise acids are called antacids.

Ionisation: The process of formation of ions in aqueous solution is called ionisation.

pH meter: An instrument used for measuring pH of a solution.

Common salt: Sodium chloride : NaCl.

Washing soda: Sodium carbonate : Na2CO3, 10H2O.

Baking soda: Sodium hydrogencarbonate : NaHCO3.

Bleaching powder: Calcium oxychloride: CaOCl2.

Plaster of Paris: Calcium sulphate hemihydrate: CaSO4. 1/2 H2O.