acid bases and salts notes

Acid, Bases and Salts Notes for Competitive Exams

Types of Acid Bases and Salts Notes

In this post, you can find an important general science topic, Acid bases and Salts notes which raise questions in exams like SSC CGL, CHSL, MTS, Railway and other government sectors exams.


Acid is the chemical compound, which produces hydrogen ions, H+ in aqueous solution, which is responsible for its acidic properties.

Properties of Acids
  • According to Bronsted-Lowry theory, Acid is a species that can donate a proton to other species.
  • Hydrogen ions present in acids make them strong and good electrolytes. 
  • Hydrogen ions cannot exist alone but combined with the water molecules.
Strong Acids
  • Examples of strong acids are hydrochloric acid, sulphuric acid, nitric acid.
Weak Acids
  •  Examples of weak acid are Formic acid, acetic acid, carbonic acid, etc.


Indicators are used to test whether the substance or compound is acidic or basic in nature. Examples of Indicators are China rose petal, Litmus, Turmeric, etc. which are found in nature.


Litmus is an acid-base indicator extracted from Lichens, a plant, which belongs to the division Thallophyta, is a widely used indicator. It has a purple colour in distilled water. When dipped into acid, it turns red. When added in a basic solution, it turns blue in colour.

Olfactory Indicators

 The substances whose odour changes when added in acidic or basic solutions are known as Olfactory Indicators.

Uses of Acids
  • Vitamin C, that is ascorbic acid, is an essential nutrient in our body.
  • Hydrochloric acid inside our stomach helps in digestion of food.
  • Sulphuric acids are used in manufacturing paints, fertilizers, synthetic fibres etc. 
  • Boric acid is used to wash our eyes.
  • Carbonic acid is used in manufacturing carbonated beverages.
  • Aqua regia, which is used by goldsmiths, in the purification of metals like gold and silver is prepared using Nitric acid. 
  • Vinegar, a dilute form of acetic acid is used as a food preservative.
List of Acids used in day to day life
Name of AcidsSources
Citric acidCitrus fruits like Oranges, grapes, limes etc.
Malic acidApple
Sour milkLactic acid
Tartaric acidTamarinds, gooseberries
Formic acidAnts and Bees
Amino acidProteins
Oxalic acidTomatoes
ascorbic acidGuava
CurdButyric acid

See also: Types of Goods in Economics

Basicity of Acids

 It is defined as the number of Hydrogen ions present in one molecule of acid.

Some of the important acids and their formulas:

Sulphuric acid H2SO4
Hydrochloric acidHCL
Nitric acid HNO3
Phosphoric acidH3PO4
Carbonic acidH2CO3

Bases and Alkalis

  • A Base is a substance that gives OH- ions in an aqueous solution. Bases are usually metal hydroxides (MOH).
  • According to Bronsted-Lowry theory, a base is any species that accepts a proton from other species.
  • Bases Soluble in water is known as alkali. All alkalis are bases but all bases are not alkali.
  • Bases are soapy and bitter in taste.
  • The strength of bases depends upon hydroxyl ions when dissolved in water.

Examples of Bases Sodium hydroxide: NaOH (caustic soda), Potassium Hydroxide: KOH (Caustic potash) etc.


The substance formed by a mixture of cation and anion is known as Salt. All part of the hydrogen of an acid is replaced by metal in it.

Uses of Salts
  • Sodium Chloride (NaCl) is used in the manufacturing of Washing Soda, Baking Soda, Caustic Soda and Chlorine.
  • Silver nitrate is used in Photography.
  • Gun Powder and Fireworks are manufactured with the help of Pottasium Nitrate.
Power of Hydrogen
  • PH scale is a scale that is used to measure, how strong or weak an acid or base is. The value in PH lies between 0 to 14. Value 7 denotes the neutrality of a substance and considered as non-reactive.
  • The value between 0 and 7 in the PH scale denotes the substance as acidic, where  0 is weakest and 6 is strongest. The value in the PH scale between 8 to 14 is Basic.
Substance PH value
Pure Water7.4
Lemon Juice2.2
Gastric Juice1.2
Acid Rain5.6
Milk of Magnesia10
Tomato Juice4.1
Baking Soda8.5
Washing Soda9.0

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