Chemistry - Acids, Bases, and Salts



  • We taste food sour and bitter, it is only because of presence of acids and bases respectively.

Litmus Solution

  • Litmus, which is extracted from lichen, has purple color (see the image given below), but the condition is when it is neither acidic nor basic, i.e. neutral.

Litmus Solution
  • Litmus basically is a plant belongs to Thallophyta, and in chemical experiment, it is commonly used as an indicator.

  • The substances, which odor changes in acidic or basic media, are known as olfactory indicators.

Acid or Base in a Water Solution

  • The hydrogen ions in HCl are produced because of the presence of water. Secondly, the separation of H+ ion from the HCl molecules cannot be done in the absence of water. The chemical formula is illustrated below

    HCl + H2O → H3O+ + Cl

  • Furthermore, hydrogen ions cannot exist alone, but they can exist in presence of water molecules. Therefore, hydrogen ions are shown as H+(aq) or hydronium ion (H3O+). The chemical formula is −

    H+ + H2O → H3O+

  • The bases which are soluble in water are known as alkalis. But all bases are not soluble in water.

  • If water is added to a concentrated acid, then the heat is generated.

  • Mixing an acid or base with the water results into decrease in the concentration of ions (i.e. H3O+/OH–) per unit volume and the process is known as dilution.

pH Scale

  • A scale, used in measuring the hydrogen ion concentration in a solution, is known as pH scale.

  • The ‘p’ in pH stands for ‘potenz’, it is a German term, which means ‘power’.

  • pH value is taken simply as a number, which indicates the acidic or basic nature of a solution. So, if the concentration of hydronium ion is higher, then the value of pH would be lower.

  • The value of pH scale ranges between ‘0’ and ’14;’ so, if pH value is measured ‘0,’ it means – it is very acidic and if it is 14, then it means – it very alkaline.

  • The neutral value of pH scale is ‘7’.

  • On a pH scale, values less than 7 represent an acidic solution and values greater than 7 represent a basic solution.

  • Usually, paper impregnated with the common indicator is used for measuring the pH (see the image given below)−

pH Scale
  • Likewise, the strength of acids and bases substance mainly depends on the number of H+ ions and OH ions produced, respectively.

  • The following image roughly illustrates (variations in color) the pH value of some of the common substances −

pH Value

Importance of pH in Everyday Life

  • The pH value of a human body ranges between 7.0 and 7.8.

  • The stomach of a human body produces hydrochloric acid that helps in the digestion of food; surprisingly, it does not harm the stomach anyway.

  • However, when the stomach produces too much acid (known as indigestion), it causes pain and irritation. To get relief from this pain, doctors suggest the use of bases known as antacids.

  • These antacids neutralize and control the increased amount of acid.

  • The teeth, which are made up of calcium phosphate, is the hardest substance in the body. However, when the pH in the mouth decreases (below 5.5), it corrodes the teeth.

  • The salt, normally, is formed by the combination of hydrochloric acid and sodium hydroxide solution; and, the combination is known as sodium chloride.

  • When the pH value of rain water is measured as less than 5.6, it is known as acid rain.

  • When acid rain flows into the rivers, then it also lowers the pH of the river water

  • The acidic river water is threat for the survival of aquatic life.

Bleaching Powder

  • Bleaching powder is produced by the action of chlorine on dry slaked lime [Ca(OH)2] and it is represented as CaOCl2.

  • Bleaching powder is normally used in textile industry, paper factory, chemical industry, and disinfecting the drinking water.

Baking Soda

  • The baking soda is commonly used in the kitchen in order to cook tasty crispy food items. It also cooks some food items faster.

  • The chemical name of baking soda is sodium hydrogencarbonate and formula is NaHCO3.

Washing Soda

  • Recrystallization of sodium carbonate results into washing soda.

  • The chemical formula of washing soda is Na2CO3.10H2O.

  • Washing soda is commonly used in glass, soap, and paper industries.

Plaster of Paris

  • Plaster of Paris is a white powder that doctors use as plaster for supporting fractured bones.

  • The chemical name of plaster of paris is calcium sulphate hemihydrate and chemical formula is 2CaSO4.H2O.