11th Chemistry NCERT notes

Stock Notations

The oxidation states of elements exhibiting variable oxidation states are specified by Roman numerals such as I, II, III, IV, etc., within parenthesis after the symbol or name of the elements. This system was introduced for the first time by German Chemist, Alfred Stock and is known as Stock notation.


Titration is procedure for determining the concentration of a solution by allowing a carefully measured volume to react with a standard solution of another substance, whose concentration is known.

Standard solution: It is a solution whose concentration is known and is taken in burette. It is also called Titrant.

There are two type of titrants:

Primary titrants/standard:

These reagents can be accurately weighed and their solutions are not to be standardised before use.
e.g., Oxalic acid, K2Cr2O7, AgNO3, CuSO4, ferrous ammonium sulphate, hypo etc.

Secondary titrants/standard:

These reagents cannot be accurately weighed and their solutions are to be standardized before use.
e.g., NaOH, KOH, HCl, H2SO4, I2, KMnO4, etc.

Types of Titrations:

  • Acid-base titrations (to be studied in Ionic equilibrium)
  • Redox Titrations

Permanganate Titrations:

  • KMnO4 is generally used as oxidising agent in acidic medium, generally provided by dilute H2SO4.
  • KMnO4 works as self-indicator persistent pink color is indication of end point.
  • Mainly used for estimation of Fe2+, oxalic acid, oxalates, H2O2 etc.



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