Question

Given, $ 4.74 \cdot gm$ of $ CuO$ when heated with current of $ {H_2}$ gives $ 3.78 \cdot gm$ of metal. Find the Equivalent mass of $ Cu$ ?

Answer 1

Hint: Equivalent weight is one equivalent mass, that is, the mass of a specified substance that binds to or exchanges with a fixed amount of another substance. Elemental equivalents are the masses combined or replaced with $ 1.008 \cdot g$ of hydrogen or $ 8.0 \cdot g$ of oxygen or $ 35.5 \cdot g$ of chlorine.

Step by step solution:
In the given problem, the oxygen is being replaced. So, the question can be solved in two steps. In the first step we need to find out the mass of oxygen in $ CuO$ and then in the second step, we will figure out the equivalent mass of copper.
Calculation of mass of oxygen in $ CuO$ -
The mass of oxygen in $ CuO$ will be equal to the difference between the total $ CuO$ and metal (copper) obtained afterwards. i.e.
$Mas{s_{oxygen}} = \left( {4.74 - 3.78} \right) \cdot g = 0.96 \cdot g$
Hence, the mass of oxygen in $ CuO$ is found to be $0.96 \cdot g$
Calculation of equivalent mass of copper –
Equivalent weight $ = 8g \cdot O \times \dfrac{{3.78 \cdot g \cdot Cu}}{{0.96 \cdot g \cdot O}} = 32 \cdot g \cdot Cu$
Hence, the equivalent weight of copper is found to be $ 32 \cdot g$ .

Note:
Equivalent weights are used in the calculation of normality. Normality of a solution is defined as the gram equivalent of solute present per liter of solution. It is denoted by the letter N.
The number of gram equivalents of solute is calculated as mass of solute in grams divided by equivalents of solute.
$ \eqalign{
  & Normality = \dfrac{{gram \cdot equivalent{s_{solute}}}}{{volum{e_{solution}}(L)}} \cr
  & number \cdot of \cdot gram \cdot equivalents = \dfrac{{mas{s_{solute}}}}{{equivalent \cdot mas{s_{solute}}}} \cr} $