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=Concept of Acids & Bases

 

Acids
Bases
Acid-Base Indicators
Olfactory indicators
pH scale
Reaction of acid with a metal
Reaction of base with a metal
How do metal carbonates and Metal Hydrogencarbonates React with metals?
Reaction of acids and bases together
Neutralisation reaction
Reaction of metallic oxide with acid
Why Acidic and basic solutions conduct electricity? Water of crystallisation
Some very important salts with their chemical name and formula

Concepts: Acids, Bases and Salts

Acids:  Those substances which when dissolved in water then produce H+ (aq) or Hydronium (H3O+) ions. They are sour in taste and change the colour of blue litmus to red. For example HCl, H2SO4, HNO3 etc.

Acid Reaction

Bases: Bases are generally metallic oxide or metallic hydroxide. When they are dissolved in water they produce OH-(aq) ions. They are bitter in taste and change the colour of red litmus to blue. For example CuO, NaOH, KOH etc.

Bases Reaction

Acid-Base Indicators: Indicators are basically dyes or mixtures which are used to detect whether the substance is acidic or basic with the help of their colour changing property. They are of two type, natural indicators and synthetic indicators. The examples of natural indicators are Litmus and turmeric. The examples of synthetic indicators are methyl orange and phenolphthalein.

Olfactory indicators: Those substances whose odour changes in acidic or basic medium are known as olfactory indicators. Some of the examples of olfactory indicators are vanilla, onion and clove.

pH scale: It is the measure of acidic or basic strength of an aqueous solution. The pH value of an acidic solution lies between 0 to 7. The pH value of a basic solution lies between 7 to 14. The pH value of a neutral substance is always 7.

Reaction of acid with a metal: When an acid reacts with a metal then Hydrogen gas is evolved along with corresponding salt.

Reaction of acid with metal

Reaction of base with a metal: When a base reacts with a metal then Hydrogen gas is evolved along with corresponding salt. Salt is composed of metal and oxygen and has negative ion.

Reaction of base with metal

How do metal carbonates and Metal Hydrogencarbonates React with Acids?
When Metal carbonates and Metal Hydrogencarbonates react with acid they form corresponding salt with carbon dioxide and water as shown in following chemical equation

Reaction of acids and bases together: Whenever acids and bases react with each other they produce salt with water. For example

reaction of acid and bases together

Neutralisation reaction: When acid and base react with each other to produce salt and water then such reaction is known as neutralisation reaction. For example

Neutralisation reaction

Reaction of metallic oxide with acid: When metallic oxide reacts with acid they produce salt along with water. For example

reaction of metal oxide with acid

Why Acidic and basic solutions conduct electricity?: Acidic and basic solutions in water conduct electricity because they produce hydrogen and hydroxide ions respectively.

Water of crystallisation: It is the definite number of molecules of water that is chemically attached to each formula unit of a salt in its crystalline form. For example washing soda (Na2CO3.10H2O) or Gypsum (CaSO4.2H2O).

Some very important salts with their chemical name and formula.

Common Name Chemical Name Chemical Formula

Baking Soda

Sodium Bicarbonate

NaHCO3

Washing Soda

Hydrated Sodium Carbonate

Na2CO3.10H2O

Plaster of paris

Calcium Sulphate hemihydrates

CaSO4.½H2O

Bleaching Powder

Calcium Oxychloride

CaOCl2

Gypsum

Calcium Sulphate dihydrate

CaSO4.2H2O



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