Preparing 500 mL of 5 M Sodium Hydroxide (NaOH) Solution: A Comprehensive Guide

Introduction

Sodium hydroxide (NaOH) is a strong base that finds extensive applications in various scientific and industrial processes. Preparing a 5 M NaOH solution in a laboratory setting is a fundamental skill. This article will guide you through the process of preparing 500 mL of a 5 M NaOH solution, including theoretical discussions and practical steps.

Theoretical Background

Molarity and Molar Concentration

Understanding the concept of molar concentration (molarity) is crucial. Molarity (M) is defined as the number of moles of solute per liter of solution. The equation to calculate molarity is:

[ M frac{n_{text{solute}}}{V_{text{solution}} (text{in liters})} ]

Where:

( n_{text{solute}} ) moles of solute ( V_{text{solution}} ) volume of the solution in liters

The units of molarity are expressed as mol/L or mol/dm3. The relationship between mass, molar concentration, and volume can be derived as:

[ text{mass of solute (g)} M times M_{text{molar}} times V (text{in liters}) ]

Where:

( M_{text{molar}} ) molar mass of the solute in g/mol ( V ) volume of the solution in liters

Molar Mass of NaOH

The molar mass of NaOH is approximately 40.00 g/mol. This value will be used in the calculations for preparing the NaOH solution.

Practical Steps to Prepare 500 mL of 5 M NaOH Solution

Step 1: Calculation of Required NaOH Mass

To prepare 500 mL of 5 M NaOH solution, the required amount of NaOH can be calculated using the formula:

[ text{Amount of NaOH (moles)} text{Molarity} times text{Volume (in liters)} ]

Given: ( text{Molarity} 5 text{ mol/L} ) ( text{Volume} 500 text{ mL} 0.5 text{ L} )

[ n_{text{NaOH}} 5 text{ mol/L} times 0.5 text{ L} 2.5 text{ moles} ]

Using the molar mass of NaOH (40.00 g/mol), the mass of NaOH required can be calculated as:

[ text{Mass of NaOH (g)} n_{text{NaOH}} times text{Molar Mass of NaOH} ]

[ text{Mass of NaOH (g)} 2.5 text{ moles} times 40.00 text{ g/mol} 100 text{ g} ]

Step 2: Weighing NaOH

Weigh out 100 grams of solid NaOH on a precision balance. It is essential to use the correct mass to achieve the desired molarity. A deviation in weight would result in an incorrect molarity.

Step 3: Dissolving NaOH in Water

Add the 100 grams of NaOH to a 500 mL volumetric flask. Pour in a small amount of distilled or deionized water to help dissolve the solid NaOH. Stir the solution to ensure complete dissolution. Utilize a magnetic stirrer or a vortex mixer for better results.

Step 4: Stoichiometric Adjustments

If the solute is not fully dissolved, add a sufficient amount of distilled or deionized water while continuously stirring until the NaOH is completely dissolved. Once the NaOH has dissolved, the solution will be thoroughly mixed.

Finally, add distilled or deionized water to the volumetric flask until the mark to achieve a total volume of 500 mL. Mix thoroughly until the solution reaches a homogeneous state.

Handling and Safety Precautions

NASOH is a strong base and can cause serious injury if not handled properly. Take the following safety measures:

Personal Protective Equipment (PPE): Wear gloves, safety goggles, and a laboratory coat. Fume Hood: Work in a fume hood to minimize the inhalation of fumes and vapors. Seal Containers: Ensure that all containers containing NaOH are sealed and stored properly to prevent contamination.

Following these steps and safety precautions will allow you to successfully prepare 500 mL of 5 M NaOH solution in a safe and efficient manner.