How to Safely Prepare a 0.5 Molar Sodium Hydroxide (NaOH) Solution- A Step-by-Step Guide

How to Prepare 0.5 Molar NaOH Solution

Preparing a 0.5 molar sodium hydroxide (NaOH) solution is a common task in various scientific and industrial applications. Sodium hydroxide, also known as lye or caustic soda, is a highly corrosive and reactive chemical that requires careful handling. In this article, we will guide you through the steps to prepare a 0.5 molar NaOH solution safely and accurately.

Materials Needed

Before you begin, gather the following materials:

– Sodium hydroxide pellets or flakes
– Distilled water
– Measuring cylinder or graduated cylinder
– Stirring rod
– Safety goggles
– Gloves
– Lab notebook

Step 1: Calculate the Amount of NaOH Needed

To prepare a 0.5 molar NaOH solution, you need to determine the amount of NaOH required. The formula for molarity is:

Molarity (M) = moles of solute / liters of solution

Since we want a 0.5 M solution, we need 0.5 moles of NaOH for every liter of solution. The molar mass of NaOH is approximately 40.00 g/mol. Therefore, for 0.5 moles, you will need:

0.5 moles NaOH x 40.00 g/mol = 20.00 g NaOH

Step 2: Weigh the NaOH

Using a balance, weigh out 20.00 grams of sodium hydroxide pellets or flakes. Be sure to wear gloves and safety goggles during this step to protect yourself from the corrosive nature of NaOH.

Step 3: Dissolve the NaOH in Water

Pour 500 milliliters of distilled water into a beaker. Gradually add the weighed NaOH to the water while stirring constantly. It is crucial to add the NaOH to the water, not the other way around, as the reaction between NaOH and water is exothermic and can cause splashing.

Step 4: Cool the Solution

After adding the NaOH, the solution may become hot due to the exothermic reaction. Allow the solution to cool to room temperature before proceeding.

Step 5: Transfer the Solution to a Measuring Cylinder

Once the solution has cooled, carefully transfer it to a 500-milliliter measuring cylinder or graduated cylinder. Be sure to use a funnel to prevent spills.

Step 6: Adjust the Volume

Add distilled water to the measuring cylinder until the solution reaches the 500-milliliter mark. Stir the solution gently to ensure it is well-mixed.

Step 7: Label and Store the Solution

Label the bottle with the concentration (0.5 M NaOH) and the date of preparation. Store the solution in a cool, dry place, away from direct sunlight and incompatible materials.

By following these steps, you can safely and accurately prepare a 0.5 molar NaOH solution for your scientific or industrial needs. Always remember to handle NaOH with care and follow proper safety protocols.