Question

An oxide of metal have $20\% $ oxygen , the equivalent weight of oxide is :
A. $32$
B. $48$
C. $40$
D. $52$

Answer 1

Hint: To calculate the equivalent weight of oxide, we need the molecular mass of oxygen and the number of electrons gained or lost in it which is also known as the n- factor.

 Complete step by step answer: Equivalent weight of a substance is defined as the weight of a substance which combines with or displaces one part by weight of hydrogen or eight parts by weight of oxygen or $35.5$ part by weight of chlorine:
It is given in the question that the metal oxide has $20\% $ oxygen , which means that $100gm$ of metal oxide contains $20gm$ of oxygen .
The equivalent weight of oxygen is 8.
Now to find out the equivalent weight of metal we use the below formula
$\dfrac{{mass{\text{ }}of{\text{ }}metal}}{{mass{\text{ }}of{\text{ oxygen}}}} = \dfrac{{equivalent{\text{ }}weight{\text{ }}of{\text{ }}metal}}{{equivalent{\text{ }}weight{\text{ }}of{\text{ oxygen}}}}$
On substituting the values in above equation , we get
$\dfrac{{80}}{{20}} = \dfrac{E}{8}$
Hence the equivalent weight of metal is $32gm$ .
Therefore , the equivalent weight of the metal oxide is
$32 + 8 = 40gm$
Hence option C is correct.

Additional Information: Equivalent weight has dimensions and units of mass, unlike atomic weight, which is dimensionless. It is determined by experiment, but now derived from molar masses. Additionally, the equivalent weight of a compound can be calculated by dividing the molar mass by the number of positive or negative electrical charges that result from the dissolution of the compound.

Note: In polymer chemistry, the equivalent weight of a reactive polymer is the mass of polymer which has one equivalent of reactivity. It is widespread to indicate the reactivity polyol, isocyanate or epoxy thermoset resins which would undergo crosslinking reactions through those functional groups.