How to Prepare 0.1N HCl from 37% HCl Solution
Preparing a 0.1N (normality) hydrochloric acid (HCl) solution from a 37% HCl stock solution is a common task in chemistry laboratories. This process involves diluting the concentrated acid to achieve the desired concentration. In this article, we will guide you through the steps to prepare a 0.1N HCl solution from a 37% HCl stock solution.
Understanding the Basics
Before we dive into the preparation process, it’s essential to understand the concepts of normality and molarity. Normality is a measure of the concentration of a solution in terms of the number of equivalents of a solute per liter of solution. In the case of HCl, one equivalent is equal to one mole of HCl. Molarity, on the other hand, is the number of moles of solute per liter of solution.
To prepare a 0.1N HCl solution, we need to dilute the 37% HCl stock solution to a concentration of 0.1 equivalents per liter. Since the molar mass of HCl is approximately 36.46 g/mol, a 0.1N solution contains 3.646 g of HCl per liter of solution.
Materials Needed
To prepare the 0.1N HCl solution, you will need the following materials:
– 37% HCl stock solution
– Distilled water
– Measuring cylinder
– Beaker
– Safety equipment (gloves, goggles, and lab coat)
– Stirring rod
Step-by-Step Instructions
1. Calculate the required volume of 37% HCl: To prepare 1 liter of 0.1N HCl, you need 3.646 g of HCl. Since the density of 37% HCl is approximately 1.18 g/mL, you can calculate the required volume of the stock solution as follows:
Volume (mL) = (mass of HCl / density of HCl) 100
Volume (mL) = (3.646 g / 1.18 g/mL) 100
Volume (mL) ≈ 30.9 mL
2. Measure the required volume of 37% HCl: Using a measuring cylinder, carefully measure out approximately 30.9 mL of the 37% HCl stock solution.
3. Add the measured HCl to a beaker: Transfer the measured HCl into a beaker containing 50-100 mL of distilled water.
4. Stir the solution: Use a stirring rod to mix the solution thoroughly. This step is crucial to ensure that the HCl is evenly distributed throughout the water.
5. Dilute to the desired volume: Once the solution is well-mixed, add distilled water to the beaker until the total volume reaches 1 liter.
6. Final adjustments: Check the pH of the solution using a pH meter or pH indicator paper. If necessary, adjust the pH to the desired level by adding small amounts of 37% HCl or distilled water.
7. Safety precautions: Always wear appropriate safety equipment (gloves, goggles, and lab coat) when handling concentrated acids. Ensure that the area is well-ventilated, and never mix water and concentrated acid directly.
By following these steps, you can successfully prepare a 0.1N HCl solution from a 37% HCl stock solution. This solution can be used in various chemical reactions and experiments, providing a reliable source of HCl for your laboratory needs.
