Preparation of 0.2 M Sodium Chloride (NaCl) Solution: A Comprehensive Guide

Understanding the process of preparing different concentrations of a solution is essential in various scientific and industrial applications. This guide will walk you through the detailed steps to prepare 500 mL of a 0.2 M sodium chloride (NaCl) solution using simple chemical and mathematical operations.

Chemical and Mathematical Background

Before starting, it's important to understand the underlying principles. The concentration of a solution is often expressed in terms of molarity (M), which is defined as the number of moles of solute per liter of solution. The formula for molarity is:

[ text{Molarity (M)} frac{text{moles of solute (n)}}{text{volume of solution in liters (L)}} ]

Step-by-Step Preparation of 0.2 M NaCl Solution

Calculate the Amount of NaCl Required: To prepare 500 mL (0.5 L) of a 0.2 M NaCl solution, you need to determine the number of moles of NaCl required. Using the formula:

[ n M times V ]

Where:

M is the molarity (0.2 M) V is the volume of the solution in liters (0.5 L)

Therefore:

[ n 0.2 , text{M} times 0.5 , text{L} 0.1 , text{moles} ]

Weight the Required Amount of NaCl: The next step is to weigh the required amount of NaCl. The molar mass of NaCl (sodium chloride) is approximately 58.44 g/mol. Using the equation:

[ text{mass} text{moles} times text{molar mass} ]

For 0.1 moles of NaCl:

[ text{mass} 0.1 , text{moles} times 58.44 , text{g/mol} 5.844 , text{g} ]

Dissolve the NaCl in Water: The final step is to dissolve the weighed NaCl in water. The process involves:

Adding 5.844 g of NaCl to a clean, dry 500 mL volumetric flask. Slowly adding distilled or deionized water to the flask until it reaches the 500 mL mark. Mixing the solution well to ensure complete dissolution of the salt.

Additional Notes and Calculations

Understanding and verifying your calculations is crucial. Using a different set of variables for additional practice or confirmation:

Convert 500 mL to liters:

[ 500 , text{mL} times frac{1 , text{L}}{1000 , text{mL}} 0.5 , text{L} ]

Solve for moles:

[ n M times V 0.2 , text{M} times 0.5 , text{L} 0.1 , text{moles} ]

Calculate the mass of NaCl required:

[ text{mass} 0.1 , text{moles} times 58.44 , text{g/mol} 5.844 , text{g} ]

The steps to follow are consistent with the previous calculations:

Take 500 mL of water in a volumetric flask.

Accurately weigh out 5.85 g of NaCl (since 1 mole of NaCl is 58.5 g, and 0.1 moles would be 5.85 g).

Add the NaCl to the volumetric flask containing the water.

Stir the solution until the NaCl is completely dissolved.

The final solution will be 0.2 M of sodium chloride in 500 mL of water.

Conclusion

Preparation of a 0.2 M NaCl solution is a fundamental laboratory skill. By following the outlined steps and calculations, you can accurately and confidently prepare a solution that meets your specific needs. Understanding the principles of molarity and the relationship between mass, moles, and volume will serve you well in many other laboratory and industrial settings.