Question

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

Answer 1

Step 1: Given data:

Given that; Initial volume of the solution,${\mathrm{V}}_1=200\mathrm{cc}$

Initial normality of solution, ${\mathrm{N}}_1=\frac{1}{2}\mathrm{N}$

final normality of solution, ${\mathrm{N}}_2=\frac{1}{10}\mathrm{N}$

Step 2: Applying the law of equivalence to calculate the volume of water:

Now, By applying the law of equivalence;

$$\begin{gathered} {\mathrm{N}}_1{\mathrm{V}}_1={\mathrm{N}}_2{\mathrm{V}}_2 \\ \Rightarrow {\mathrm{V}}_2=\frac{{\mathrm{N}}_2{\mathrm{N}}_1}{{\mathrm{V}}_2} \\ =1000\mathrm{cc} \end{gathered}$$

Step 3: final volume of water added to the solution:

The final volume of water added,

$$\begin{gathered} \mathrm{V}={\mathrm{V}}_2-{\mathrm{V}}_1 \\ =(1000-200)\mathrm{cc} \\ =800\mathrm{cc} \end{gathered}$$

Hence, the volume of water that needs to be added to the solution is $800\mathrm{cc}$.