- Dilution is a process of adding water to the standard solution lowered the concentration of the solution.
- In dilution of solution, we should take note that mole of solute before dilution is equal to the mole of solute after dilution.
\[\frac{{{M_1}{V_1}}}{{1000}} = \frac{{{M_2}{V_2}}}{{1000}}\]
or
\[{M_1}{V_1} = {M_2}{V_2}\]
M1 = Molarity before dilution
M2 = Molarity after dilution
V1 = Volume before dilution
V2 = Volume after dilution
Example 1
100cm3 of 0.5 mol dm-3 sodium chloride solution is diluted with distilled water to produce 250 cm3 of solution. Calculate the concentration (in mol dm-3) of the sodium chloride solution after the dilution.
Answer:
M1 = 0.5 mol dm-3
M2 = ?
V1 = 100cm3
V2 = 250 cm3
\[\begin{gathered}
{M_1}{V_1} = {M_2}{V_2} \hfill \\
(0.5)(100) = {M_2}(250) \hfill \\
{M_2} = \frac{{(0.5)(100)}}{{(250)}} \hfill \\
{M_2} = 0.1mold{m^{ – 3}} \hfill \\
\end{gathered} \]
Example 2
Find the volume of 2 mol/dm3 nitric acid that needs to be diluted with distill water to produce 500cm3 of 0.05 mol/dm3 nitric acid.
Answer:
M1 = 2 mol dm-3
M2 = 0.05 mol/dm3
V1 = ？
V2 = 500 cm3
\[\begin{gathered}
{M_1}{V_1} = {M_2}{V_2} \hfill \\
(2){V_1} = (0.05)(500) \hfill \\
{V_1} = \frac{{(0.05)(500)}}{{(2)}} \hfill \\
{V_1} = 12.5c{m^{ – 3}} \hfill \\
\end{gathered} \]