Indicators
Types of Indicators
Natural indicators
Olfactory indicators
Substances which change their smell when mixed with acid or base are known as Olfactory Indicators.Synthetic indicators
Indicators that are synthesized in the laboratory are known as Synthetic Indicators. For example; Phenolphthalein, methyl orange, etc.
Acids
Acids are sour in taste, turn blue litmus red, and dissolve in water to release H+ ions.
Example: Sulphuric acid (H2SO4), Acetic Acid (CH3COOH), Nitric Acid (HNO3) etc.
Acids are classified into two categories - Natural acids and Mineral acids.
Properties of Acids
- Acids have a sour taste.
- Turns blue litmus red.
- Acid solution conducts electricity.
- Release H+ ions in aqueous solution.
Bases
Bases are bitter in taste, have soapy touch, turn red litmus blue and give hydroxide ions (OH–) in aqueous solution.
Examples: Sodium hydroxide (caustic soda) – NaOH
Calcium hydroxide – Ca(OH)2
Potassium hydroxide (caustic potash) – (KOH)
Bases are classified into two categories - Water soluble and Water insoluble.
Salts
Salts are the ionic compounds which are produced after the neutralization reaction between acid and base.
Salts are electrically neutral.
Characteristics of Salt
- Most of the salts are crystalline soild.
- Salts may be transparent or opaque.
- Most of the salts are soluble in water.
- Solution of the salts conducts electricity in their molten state also.
- The salt may be salty, sour, sweet, bitter and umami (savoury).
- Neutral salts are odourless.
- Salts can be colourless or coloured.
The topics discussed in this chapter are as follows:
- Ionisable and non-ionisable compounds
- Arrhenius theory of acids and bases
- Bronsted Lowry theory
- Dilution
- Universal indicator
- Importance of pH in everyday life
- Manufacture of Acids and Bases
