Chapter 14.2, Problem 35SSC

Interpretation Introduction

Interpretation:

The laboratory method is to be described for the preparation of a specific volume of a dilute from a concentrated stock solution.

Concept Introduction:

Stock solution:

Concentrated solutions of known molarities are known as a stock solution.

For example:

A concentrated solution of hydrochloric acid of 10 molarity is 10M.

Dilution is the process of decreasing the concentration of a stock solution by adding more solvent to the solution. The solvent added is usually the universal solvent, known as water. The more solvent you add, the more diluted the solution will get.

In dilution, the amount of solute does not change, the number of moles is the same before and after dilution.

If subscript "1" represents initial and "2" represents the final values of the quantities involved, we have:

  $n_1 =M_1 \times V_1 \text{ and} n_2=M_2 \times V_2$

Here, molarity is used as a unit of concentration and n₁ and n₂ are the number of moles before and after dilution respectively.

  $n_1 =n_2$

And thus,

The equation for dilution is

  $\begin{array}{l} M_1{V}_1=M_2{V}_2\hfill \\ Stocksolution=Dilutedsolution\hfill \end{array}$

Where,

M₁= molarity of the stock solution

V₁= volume of stock solution

M₂= molarity of the diluted solution

V₂= volume of diluted solution

Answer to Problem 35SSC

To prepare dilute solution from a stock solution, first, the volume of the stock solution needed is calculated and taken in a volumetric flask. Then water is added to the calibration line of the volumetric flask.

Explanation of Solution

To prepare dilute solution from a stock solution, first, the volume of stock solution needed is calculated using the following equation:

The equation for dilution is $M_1{V}_1=M_2{V}_2$

Stock solution = Diluted solution

Where

M₁= molarity of the stock solution

V₁= volume of stock solution

M₂= molarity of the diluted solution

V₂= volume of diluted solution

From this equation, V₁is calculated, that is, the volume of stock solution needed:

= $\mathrm{Volume}ofstocksolution(V_1)=\frac{M_2{V}_2}{M_1}$

Where,

M₁= Molarity of the stock solution

V₁= Volume of stock solution

M₂= Molarity of the diluted solution

V₂= Volume of diluted solution

After the volume calculation, this volume is added to the volumetric flask.

Then water is added to the calibration line of the volumetric flask.