Simple Solution

Solution Preparation

A solution is a homogenous mixture of two or more substances.

It consists of a solute (the substance being dissolved) and a solvent (the substance doing the dissolving).

Key Concepts

Solute: The component present in a lesser amount that is dissolved in the solvent.

Solvent: The component present in a larger amount that dissolves the solute.

Concentration: The amount of solute present in a given amount of solution, expressed in units such as molarity (M), molality (m), per cent by mass, or parts per million (ppm).

Materials Needed

• Solute (e.g., NaCl, glucose).

• Solvent (typically water, but can be other liquids).

• Volumetric flask (of appropriate volume for desired concentration).

• Beaker (for pre-dissolving).

• Weighing balance (accurate to the required precision).

• Spatula.

• Funnel.

• Distilled or deionised water.

Steps for Preparing a Simple Solution

Calculate the required mass of solute:

Determine the desired concentration and volume of the solution.

Use the formula: \text{Mass of solute} = \text{Desired concentration} \times \text{Desired volume} \times \text{Molar mass of solute}

Example: To prepare 100 mL of a 1.0 M NaCl solution:

Molar mass of NaCl = 58.44 g/mol

Volume = 100 mL = 0.1 L

Mass of NaCl = 1.0 \frac{\text{mol}}{\text{L}} \times 0.1 \text{ L} \times 58.44 \frac{\text{g}}{\text{mol}} = 5.844 \text{ g}

Weigh the solute:

Accurately weigh the calculated mass of the solute using a weighing balance.

Use a clean, dry container (e.g., a weighing boat or beaker).

Dissolve the solute:

Transfer the weighed solute into a clean beaker.

Add a small amount of the solvent (less than the final desired volume) to the beaker.

Stir the mixture gently until the solute is completely dissolved.

Transfer to a volumetric flask:

Using a funnel, carefully transfer the solution from the beaker into the volumetric flask.

Rinse the beaker with small portions of the solvent and add the rinsings to the flask to ensure all the solute is transferred.

Add solvent to the mark:

Add the solvent to the volumetric flask until the solution reaches the calibration mark on the flask.

Ensure the bottom of the meniscus aligns with the mark at eye level.

Mix thoroughly:

Stopper the flask and invert it several times to ensure the solution is homogeneous.

Example Calculation

Problem: Prepare 250 mL of a 0.2 M solution of glucose (C₆H₁₂O₆).

Molar mass of glucose = 180.16 g/mol

Volume = 250 mL = 0.250 L

Mass of glucose = 0.2 \frac{\text{mol}}{\text{L}} \times 0.250 \text{ L} \times 180.16 \frac{\text{g}}{\text{mol}} = 9.008 \text{ g}

Dissolve 9.008 g of glucose in less than 250 mL of water, then add water until the total volume is 250 mL in a volumetric flask.