Question

Equivalent weight of $KCl.MgC{l_2}.6{H_2}O$ is:
A. M
B. $\dfrac{M}{2}$
C. $\dfrac{M}{3}$
D. 2M

Answer 1

We know that the equivalent weight of an element or radical is equal to its atomic weight or formula weight divided by the valence it assumes in compounds. The unit of equivalent weight is the atomic mass unit. Equivalent weight is the weight of a compound that contains one equivalent of a proton (for acids) or one equivalent of a hydroxide (for bases).
${\text{Equivalent weight = }}\dfrac{{{\text{Molecular weight}}}}{{{\text{No}}{\text{. of electrons gained or lost}}}}$
Molecular mass is calculated as the sum of the atomic weights of each individual element constituting a molecule.

Complete step by step answer:
To solve this question, first we need to understand some important terms. The amount of a substance in grams numerically equal to the equivalent weight is called a gram equivalent. Molecular weight, also called molecular mass, mass of a molecule of a substance, based on 12 as the atomic weight of carbon-12. It is calculated in practice by summing the atomic weights of the atoms making up the substance's molecular formula.
Also, the molecular mass is the mass of different molecules of the same compound may have different molecular masses because they contain different isotopes of an element.
Oxidation state indicates the degree of oxidation for an atom in a chemical compound; it is the hypothetical charge that an atom would have if all bonds to atoms of different elements were completely ionic. Oxidation states are typically represented by integers, which can be positive, negative, or zero.
Let’s consider the molecular weight as M
As we know that oxidation state of $Mg$ = $+ 2$
${\text{Equivalent weight = }}\dfrac{{{\text{Molecular weight}}}}{{{\text{No}}{\text{. of electrons gained or lost}}}}$
Substituting the known values we get,
Therefore, equivalent weight = $\dfrac{M}{2}$.

So, the correct answer is Option B.

Note: We must remember that the difference between equivalent weight and molecular weight is that the proportional mass of a chemical entity which combines or displaces other chemical entities. Equivalent weight can be defined as the mass of an element or compound or an ion which combines or displaces 1 part of hydrogen or 8 parts of oxygen or 35.5 parts of chlorine by mass.