Question

What volume of distilled water must we add to $50mL$ of a $20\% $ solution to get concentrations of $15\% $ , $10\% $ and $5\% $ ?

Answer 1

Hint: A drop in the pH of a chemical, which can be a gas, vapour, or solution, is referred to as dilution. It is the procedure for lowering the concentration of a solute in a solution by mixing it with the solvent. Add more solvent without adding more solute to dilute a solution. To ensure that all parts of the solution are even, thoroughly mix the resultant solution.
Formula Used-
${C_1}{V_1} = {C_2}{V_2}$
${C_1} = $ Concentration of stock solution
${C_2} = $ Final concentration of stock solution
${V_1} = $ denotes the Volume of stock solution needed to make the new solution
${V_2} = $ the final volume of the solution

Complete answer:
Using the dilution formula,
${C_1}{V_1} = {C_2}{V_2}$
Rearranging the formula, we get,
${V_2} = {V_1} \times \dfrac{{{c_1}}}{{{c_2}}}$
For $15\% $ concentration,
${V_2} = 50mL \times \dfrac{{20\% }}{{15\% }} = 67mL$
The final volume is $67mL$ .
$67mL - 50mL = 17mL$.
Hence, $17mL$ of distilled water must be added to $50mL$ of a $20\% $ solution to get concentrations of $15\% $.
For $10\% $ concentration,
${V_2} = 50mL \times \dfrac{{20\% }}{{10\% }} = 100mL$
$100mL - 50mL = 50mL$
Hence, $50mL$ of distilled water must be added to $50mL$ of a $20\% $ solution to get concentrations of $10\% $.
For $5\% $ concentration,
${V_2} = 50mL \times \dfrac{{20\% }}{{5\% }} = 200mL$
$200mL - 50mL = 150mL$
Hence, $150mL$ of distilled water must be added to $50mL$ of a $20\% $ solution to get concentrations of $5\% $ .

Note:
A solution concentration is a measurement of how much solute has dissolved in a specific amount of solvent or solution. A concentrated solution is one that has a large amount of dissolved solute. A dilute solution is one that has a small amount of dissolved solute in it.