**OVERVIEW**

A 50% (w/w) Sodium Hydroxide can be purchased from several commercial suppliers. It is a clear colorless liquid and can be diluted to prepare solutions of known concentrations. Here we describe a procedure to prepare a 10 M NaOH solution using commercially supplied 50% stock solution. Remember that the molarity of Sodium Hydroxide is equal to the normality of the solution, which means a 10M solution is also a 10N solution.

**REQUIREMENTS**

**Reagents and solutions**50% (w/w) sodium hydroxide solution

Distilled water

**Equipment and disposables**Measuring cylinder/volumetric flask

Beaker (1 Liter)

Magnetic stirrer

**OBJECTIVE**

Preparation of 1 Liter of 1M Sodium Hydroxide solution from 50% (w/w) concentrated Stock Solution

**PROCEDURE: **

**Use personal protective equipment (lab coat, gloves, goggles etc) for your safety and follow the guidelines of your institute.**

**PART I: Calculate how much 50% (w/w) concentrated Sodium Hydroxide Solution is required to prepare 1 L of 10M NaOH solution**

**Step 1: Calculate the molarity of 50% (w/w) concentrated Sodium Hydroxide solution**The procedure to calculate molarity of 50% (w/w) concentrated Sodium Hydroxide solution is described in detail in the post “Molarity of 50% (w/w) Sodium Hydroxide (NaOH)”.

From this post, you will know that the molarity of 50% (w/w) concentrated Sodium Hydroxide solution is 18.94 M.

**Step 2: Calculate how much concentrated stock solution is required to prepare 1L of 1M Sodium Hydroxide solution using dilution method.**Dilution method is described in the post “Preparing Working Solution from Stock Solution by Dilution”

Use the following formula to calculate the volume of concentrated stock solution required for the preparation of 1 liter of 1M Sodium Hydroxide solution.

Formula: C_{f} x V_{f} = C_{S} x V_{S}

C_{f} (concentration of diluted (final) solution) = 10 M

V_{f} (volume of diluted (final) solution) = 1 liter

C_{S} (concentration of stock solution) = 18.94 M

V_{S} (volume of stock solution) = ? (unknown)

Place all values in the formula:

10 x 1 = 18.94 x VS

VS = 10 x 1/ 18.94 = 0.528 liter

So you need 0.528 liter of 50% (w/w) concentrated Sodium Hydroxide solution to prepare a 1 liter of 1M Sodium Hydroxide solution.

**Step 3 (optional): Calculate the volume of solvent to be taken.**

Final volume of diluted solution = 1 Liter

Volume of concentrated solution = 0.528 liter

Volume of solvent (water) required = 1 – 0.528 = 0.472 liter

So you need to mix 0.528 liter (i.e., 528 ml) of concentrated solution to 0.472 liter (472 ml) water to prepare 1 liter of 10 M Sodium Hydroxide solution.

## PART II: Solution preparation

**Step 4: Transfer 528 ml of 50% NaOH stock solution in a beaker/volumetric flask/measuring cylinder. Add 472 ml water and mix it to prepare a homogeneous solution.**Note: In case you have not calculated the amount of water to be added, just take 528 ml of 50% NaOH stock solution in a 1 liter measuring cylinder or volumetric volume flask and add water to bring the final volume to 1 Liter and mix it.

**STORAGE **Solution can be stored at room temperature.

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