Mole concept is an important tool for dealing with chemical calculations. The element have atomic mases while compounds have molecular masses or molar masses. Mole is infact, a collection of Avogadro's number `(N_(A))` of the particles of a substance whether element or compound. The value of Avogadro's number is `6.022 xx 10^(23)`
(a) Why is mole commonly called chemist's dozen ?
(b) What is the value associated with the term mole ?

Explanation

(a) Just as a dozen represents 12 articles, a mole represents `6.022 xx 10^(23)` or Avogadro's number of particles. Therefore, it has been rightly called chemist's dozen.
(b) Since particles such as atoms, ions and molecules are very extremely small in size, it is very difficult to identify and express them individually. These are collectively represented as mole. For example, `3.011 xx 10^(23)` molecules of `CO_(2)` gas are shown as 0.5 mole which is very simple.