Solution Preparation

Mole

A counting term in chemistry representing 6.022 x 10²³ entities, used for measuring amounts of substances.

Concentration

The amount of solute present in a given volume of solution, commonly expressed in molarity (M).

Molarity (M)

Defined as the number of moles of solute per liter of solution.

Preparation of Sodium Chloride Solution

The process of preparing a sodium chloride solution with specified concentration and volume.

How do you calculate the amount of sodium chloride needed for a 0.25 M solution in 500 mL?

0.25 moles/L x 0.5 L = 0.125 moles; then 0.125 moles x 58.44 g/mole = 7.34 g.

What is the total mass of sodium chloride required for 500 mL of a 0.25 M solution?

7.34 g.

Why should you not return excess reagent to the original container?

To avoid contamination and maintain the integrity of the original substance.

What is the process for dissolving sodium chloride in a volumetric flask?

Transfer the sodium chloride to the flask, add water to dissolve, then fill to the 500 mL mark.

Final Concentration Calculation

Measured mass (7.34 g) divided by molar mass (58.44 g/mole) gives moles; this divided by volume (0.5 L) gives final concentration.

What is the resulting concentration of the prepared sodium chloride solution?

Approximately 0.251 M.

Importance of labeling and storage

Clearly label the storage container with contents and concentration for safety.