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Acids Bases
– Sour in taste– Bitter in taste
– Change the blue litmus to red– Change red litmus to blue
– eg.HydrochloricAcidHCleg. Sodiumhydroxide NaOH
– SulphuricAcidH2SO4PotassiumhydroxideKOH
– NitricAcidHNO3 CalciumhydroxideCa(OH)2
– AceticAcid CH3 COOH– AmmoniumhydroxideNH4OH

                                                     

 Some Naturally occuring acids
Vinegar –Acetic Acid
Orange –Citric Acid
Lemon –Citric Acid
Tamarind –Tartaric Acid
Tomato – OxalicAcid
Sour milk (Curd) –Lactic Acid
Ant and Nettle sting –Methanoic Acid

Acid – Base Indicators – Indicate the presence of an acid or base in a
solution.
Litmus solution – It is a natural indicator. It is a purple day extracted from
Lichens. Other examples are Red Cabbage and coloured petals of Petunia
and turmeric.
Olfactory indicators – Show odour changes in acidic or basic media. eg. onion and clove.

Dilute Acid : Contains only a small amounts of acid and a large amount of
water.
Concentrated Acid : A concentrated acid contains a large amount of acid and a small amount of water.
Chemical Properties of Acids and Bases
Acid + Metal --> Salt + Hydrogen

Pop test : When a burning candle is brought near a test tube containing hydrogen gas it burns with a ‘Pop’ sound. This test is conducted for examining the presence of hydrogen gas.

Base + Metal --> Salt + Hydrogen
NaOH + Zn --> Na2ZnO2 + H2
                  Sodium Zincate
Note – Such reactions are not possible with all the metals.

Strength of an Acid or Base
Strength of acids and bases depends on the no. of H+ions and OH–ions
produced respectively.
With the help of a universal indicator we can find the strength of an acid or
base. This indicator is called PH scale.
pH = Potenz in German means power.
This scale measures from 0 (very acidic) to 14 (very alkaline) 7 Neutral
(water in Neutral).
pH paper : Is a paper which is used for measuring PH.

– strong Acids give rise to more H+ions.
eg. HCl, H2SO4 and HNO3.
– Weak Acids give rise to less H+ ions
eg. CH3 COOH, H2 CO3 (Carbonic acid)
– Strong Bases – Strong bases give rise to more OH– ions.
eg. NaOH, KOH, Ca(OH)2
– Weak Bases : give rise to less OH– ions.
eg. NH4OH

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Importance of pH in our daily life

  • Importance of pH in our digestive system – pH level of our body regulates our digestive system. In case of indigestion our stomach produces acid in a very large quantity because of which we feel pain and irritation in our stomach.
  • To get relief from this pain antacids are used. These antacids neutralises the excess acid and we get relief.
  • pH of Acid Rain : When pH of rain water is less than 5.6 it is called Acid Rain.When this acidic rain flows into rivers these also get acidic, which causes a threat to the survival of aquatic life.
  • pH of Soil : Plants require a specific range of pH for their healthy growth. If pH of soil of any particular place is less or more than normal than the farmers add suitable fertilizers to it.
  • Our body functions between the range of 7.0 to 7.8 living organisms can survive only in the narrow range of pH change.
  • Tooth decay and pH : Bacteria present in the mouth produce acids by degredation of sugar and food particles remaining in themouth. Using toothpaste which is generally basic can neutralise the excess acid and prevent tooth decay.
  • Bee sting or Nettle sting contains methanoic acid which causes pain and irritation. When we use a weak base like baking soda on it we get relief.

Neutral Salts : Strong Acid + Strong base
pH value is 7
eg. NaCl, CaSO4
Acidic Salts : Strong Acid + weak base
pH value is less than 7
eq. NH4Cl, NH4 NO3
Basic Salts : Strong base + weak acid
pH value is more than 7
eg. CaCO3, CH3 COONa

Chemicals from Common Salt
– Sodium chloride is called as common salt used in our food. It is derived
from seawater.
– Rock Salt is the brown coloured large crystals. This s mined like coal.
– Common Salt is an important raw material for many materials of daily use
such as.
Sodium hydroxide
Washing Soda
Bleaching Power.

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