Indicators
Types of Indicators
Natural indicators
Olfactory indicators
Substances which change their smell when mixed with acid or base are known as Olfactory Indicators. For example; Onion, vanilla etc.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