Definition Of Bases

Definition Of Bases

A base is a substance that, in aqueous solution, is slippery to the touch, tastes bitter, changes the colour of indicators, reacts with acids to form salts, and promotes certain chemical reactions

More About Bases

  • Examples of bases are the hydroxides of the alkali and alkaline earth metals (NaOH, Ca (OH) 2, etc.)
  • Bases produce hydroxide ions 0H- in aqueous solutions, and are thus classified as Arrhenius bases
  • For a substance to be classified as an Arrhenius base it must produce hydroxide ions in solution—in order to do so, Arrhenius believed the base must contain hydroxide in the formula
  • Arrhenius theory cannot explain the basic properties of aqueous solutions of ammonia (NH3) or its organic derivatives
  • According to Bronsted–Lowry acid–base theory, a base is a substance that can accept hydrogen ions ( H+) —otherwise known as protons
  • In the Lewis model, a base is an electron pair donor
  • When added to water, bases give solutions with a hydrogen ion activity lower than that of pure water, i.e., a pH higher than 7.0 at standard conditions
  • A soluble base is called an alkali if iy releases 0H) - ions
  • Basicity is not the same as alkalinity
  • Metal oxides, hydroxides, and especially alkoxides are basic, and counter anions of weak acids are weak bases
  • Bases reduce hydrogen ion concentration in water
  • A reaction between an acid and base is called neutralization
  • In a neutralization reaction, an aqueous solution of a base reacts with an aqueous solution of an acid to produce a solution of water and salt in which the salt separates into its component ions
  • If the aqueous solution is saturated with a given salt solute, any additional such salt precipitates out of the solution
  • Slimy or soapy feel on fingers, due to saponification of the lipids in human skin
  • Concentrated or strong bases are caustic on organic matter and react violently with acidic substances
  • Aqueous solutions or molten bases dissociate in ions and conduct electricity
  • Reactions with indicators: bases turn red litmus paper blue, phenolphthalein pink; keep bromo thymol blue in its natural colour of blue, and turn methyl orange yellow
  • The pH level of a basic solution is higher than 7
  • Bases are bitter in taste

Uses of Bases

  • Sodium hydroxide is used to manufacture soap. It is used in petroleum-refining; in making medicines, paper, pulp
  • Calcium hydroxide is also known as slaked lime. It is used to neutralize acid in water supplies; in the manufacture of bleaching powder; as a dressing material for acid burns; as an antidote for food poisoning; in the preparation of fungicides and in the mixture of whitewash
    • Ammonium hydroxide is used to remove ink spots from clothes and to remove grease from window-panes
    • Alkalis are used in alkaline batteries