Question

Identify the correct descending order of equivalent weights:
I) \[{\text{Ag}}\]
II) \[{\text{H}}\]
III) \[{\text{Cu}}\]
IV) \[{\text{Zn}}\]
A. I, IV, III, II
B.I,III,IV,II
C.I,II,IV,III
D.IV,II,III,I

Answer 1

Hint: The equivalent weight of a solution is given as the molecular weight of the solute that is divided by the valency of the solute. Equivalent weight is used for calculating the mass of a substance in laboratory analysis, mostly titration.

Complete step by step answer:
We know that the formula of equivalent weight is given as,
\[\therefore {\text{Equivalent}}\,{\text{weight}}\, = \,\dfrac{{{\text{M}}{\text{.W}}}}{{{\text{N}} - \,{\text{factor}}}}\]
Here, \[{\text{M}}{\text{.W}}\]= molecular weight
\[{\text{N - Factor}}\]= valency factor.
Now, we will calculate the equivalent weight of \[{\text{Ag}}\],\[{\text{H}}\],\[{\text{Cu}}\]and \[{\text{Zn}}\].
We know that valency of silver is +1 and molecular weight is 108.
So, equivalent weight of\[{\text{Ag}} = \,\dfrac{{108}}{1} = 108\]
We know that valency of zinc is +2 and molecular weight is 66.
So, equivalent weight of \[{\text{Zn}} = \dfrac{{66}}{2} = \,33\]
We know that valency of copper is +2 and molecular weight is 64
So, equivalent weight of \[{\text{Cu}} = \dfrac{{64}}{2} = \,32\]
We know that valency of hydrogen is +1 and molecular weight is 1.
So, equivalent weight of \[{\text{H}}\, = \,\dfrac{1}{2} = \,0.5\]
Therefore, the correct descending order of equivalent weights is \[{\text{Ag}}\,{\text{ > }}\,{\text{Zn}}\,{\text{ > }}\,{\text{Cu > }}\,{\text{H}}\]

So, the correct answer is Option A .

Note:
Students may get confused between molecular weight and equivalent weight. The molecular weight of a compound is calculated by adding the molar masses of all the constituent atoms. It is the mass of an element divided by the amount of the given substance. Equivalent weight is calculated by dividing the molecular weight by that of the valency.