Question

Equivalent weight of ferrous ion is (Atomic weight of \[{\rm{Fe = 56}}\]):
(A) \[{\rm{56}}\]
(B) \[28\]
(C) \[14\]
(D) \[32\]
.

Answer 1

Hint:
As we know that the ions are represented by cation or anion. The cation or anion carry charges. According, to the cation or anion charges the compound gets naming. For example- if any element is bonded with maximum number of oxygen, it gets its suffix as -ic and if it is bonded with minimum number then it will be named as-ous.

Complete step by step solution
Let’s first discuss the definition of equivalent weight.
Equivalent weight-it is the mass of a compound which undergoes dissociation or association when reacts with another compound of definite mass. It is the ratio of molar mass of compound to the total charge on cation or total charge on anions .it is represented by unit gram-equivalent.

Mathematically, it is expressed as follows;
\[{\rm{Equivalent}}\;{\rm{weight = }}\dfrac{{{\rm{molar}}\,{\rm{mass}}}}{{{\rm{total}}\,{\rm{charge}}\,{\rm{on}}\,{\rm{cation}}\,{\rm{or}}\,{\rm{total}}\,{\rm{charge}}\,{\rm{on}}\,{\rm{anion}}}}\]
The given question is to calculate ferrous ion-
Let’s calculate by using the above formula as follows;
The ferrous ion is the name of iron when it has \[{\rm{ + 2}}\] oxidation state. The -ous suffix comes when iron is bonded with a minimum number of oxygen (\[{\rm{FeO}}\]).
Now, the iron contains total charge as \[{\rm{ + 2}}\] so,
The equivalent weight we get as-
\[
{\rm{Equivalent}}\;{\rm{weight}} = \dfrac{56 \, {\rm{g/mol}}}{2}
 = 28\,{\rm{gram\, equivalents}}
\]

Therefore, the equivalent weight of ferrous ions is \[28\].
So we can say that the correct option is option (B).

Note:
By calculating equivalent weight we can calculate normality of any compound in a given solution. Normality is defined as the number of gram equivalents of the solute is dissolved per litre of the solution.