Question

How much water should be added to 200 cc of semi normal solution of $\mathrm{NaOH}$ to make it exactly decinormal?

Answer 1

Step 1: Given data

The volume of semi-normal $\mathrm{NaOH}$ solution$=200\mathrm{cc}$

Step 2: To find the volume of $\mathrm{NaOH}$ to make it decinormal.

We know the Normality equation i.e.
$\underset{\mathrm{Initial}\mathrm{solution}}{{\mathrm{N}}_1{\mathrm{V}}_1}=\underset{\mathrm{Final}\mathrm{Solution}}{{\mathrm{N}}_2{\mathrm{V}}_2}$
Here, ${\mathrm{N}}_1\mathrm{and}{\mathrm{N}}_2$are the normality of initial and final solutions and ${\mathrm{V}}_1\mathrm{and}{\mathrm{V}}_2$ are the volumes of initial and final solutions.

Substituting the values in the normality equation we get,
$(\frac{1}{2}\mathrm{x}200)=(\frac{1}{10}\mathrm{x}{\mathrm{V}}_2)$
$100=\frac{{\mathrm{V}}_2}{10}$

The volume of the final solution ${\mathrm{V}}_2=1000\mathrm{cc}$

The volume of water added = $1000\mathrm{cc}-200\mathrm{cc}$$\Rightarrow 800\mathrm{cc}$

Therefore, the volume of water added $=800\mathrm{cc}$