Question

The oxide of a metal contains 40% oxygen, by weight. What is the equivalent weight of the metals?
a) 24
b) 12
c) 40
d) 36

Answer 1

Hint: Equivalent weight is the mass of one equivalent, that is the mass of a given substance which will combine with or displace a fixed quantity of another substance.

Complete answer:
Given, an oxide of a metal contains 40 % oxygen by weight.
Percentage of oxide in the compound = 40 %
Therefore, Percentage of metal in the given compound = 100 - 40 = 60 %
Let us suppose the mass of the given metal oxide to be 100 g.

We know that Equivalent weight of a metal = ${\dfrac{Mass\;of\;metal}{Mass\;of \;Oxygen}}\times {Equivalent \;weight \;of \;Oxygen}$
Thus, Equivalent weight of the metal in the given metal oxide,
= ${\dfrac{Mass\;of\;metal}{Mass\;of\;Oxygen}}\times {Equivalent\;weight\;of\;Oxygen}$
= ${\dfrac{60}{40}} \times {8}$
= 12
[Because the Equivalent weight of oxygen is 8]
Thus, the equivalent weight of the metal is 12.

Hence, the required option for the given question is b)12.

Additional Information The equivalent weight of an element is the mass which combines or displaces 1.008 gram of hydrogen or 8.0 grams of oxygen or 35.5 grams of chlorine.

Note: In the given question, the percentage of oxide in the metal oxide is given. Considering the whole metal oxide to be 100 g, we can find out the percentage of the metal in the oxide. With the percentage of metal and the percentage of oxide in the metal oxide, we can find the equivalent weight of the metal with the help of the formula of equivalent weight.