Question

The equivalent weight of iron in ferric chloride is ( At. Wt. Of $ Fe = 55.8 $ ).

Answer 1

Hint :The equivalent weight can be calculated from the molecular weight and valency of salt. A salt can be dissociated into ions easily. The charge on the ions of salt can be written as the valency of the salt. The molecular weight of the solute divided by the valency of salt gives the equivalent weight of atoms.

Complete Step By Step Answer:
Given salt is ferric chloride, the molecular formula of ferric chloride is $ FeC{l_3} $
Ferrous is the element with atomic number $ 26 $ and chlorine is the element with atomic number $ 17 $ .
The iron has the $ + 3 $ oxidation state, thus this salt was named as ferric chloride. If the iron has $ + 2 $ oxidation state the salt was named as ferrous chloride.
Given that ferrous atomic weight is $ 55.8gm{\left( {mol} \right)^{ - 1}} $
The equivalent weight of iron can be obtained by dividing the molecular weight of the atom by the valency of the salt, here the salt has a valency of $ + 3 $ .
Thus, the equivalent weight will be
 $ Equivalent\;weight = \dfrac{{molecular\;weight}}{{valency}} $
Substitute the values of molecular weight of iron and valency of ion in the above formula,
We will get
 $ Equivalent\;weight = \dfrac{{55.8}}{3} = 18.6 $
Thus, the obtained equivalent of iron in ferric chloride is $ 18.6 $
The equivalent weight has no units, but when expressed in grams it can be called as gram equivalent weight.

Note :
Given a chemical compound containing one ferrous atom and three chlorine atoms, it is an inorganic salt. The charge on the iron is $ + 3 $ and the charge on each chlorine atom is $ - 1 $ , thus the three chlorine atoms have a charge of $ - 3 $ . Thus, the charges on the positive and negative ions were balanced and the salt has a valency of $ + 3 $ .