How to Safely Prepare a 1N Hydrochloric Acid Solution from Concentrated HCl

How to Prepare 1N HCl from Conc HCl

Preparing a 1N (Normal) solution of hydrochloric acid (HCl) from concentrated HCl is a common laboratory task. This process involves diluting the concentrated acid to achieve the desired normality. Here, we will discuss the step-by-step procedure to prepare a 1N HCl solution from concentrated HCl.

Understanding the Basics

Before diving into the preparation process, it is essential to understand the concepts of normality and molarity. Normality is defined as the number of equivalents of a solute per liter of solution. In the case of HCl, it is a monoprotic acid, meaning it donates one hydrogen ion (H+) per molecule. Therefore, the normality of a HCl solution is the same as its molarity.

Concentrated HCl typically has a concentration of 37% (w/w) and a density of approximately 1.19 g/mL. This means that in 1 mL of concentrated HCl, there are about 1.19 g of HCl. To prepare a 1N HCl solution, we need to dilute the concentrated acid to a specific volume that will result in 1 equivalent of HCl per liter of solution.

Materials Needed

To prepare a 1N HCl solution from concentrated HCl, you will need the following materials:

– Concentrated HCl (37% w/w)
– Distilled water
– Measuring cylinder
– Safety equipment (gloves, goggles, lab coat)
– Stirring rod
– Beaker

Step-by-Step Procedure

1.

Calculate the required volume of concentrated HCl

To prepare 1N HCl, you need to dilute 1 equivalent of HCl to 1 liter of solution. Since HCl is a monoprotic acid, the equivalent weight is equal to its molar mass, which is approximately 36.46 g/mol. To calculate the required volume of concentrated HCl, use the following formula:

Volume of concentrated HCl (mL) = (Molarity of desired solution) × (Molar mass of HCl) × (Density of concentrated HCl) / (Concentration of concentrated HCl)

For a 1N HCl solution, the molarity is 1N, and the concentration of concentrated HCl is 37% (w/w). Plugging in the values, we get:

Volume of concentrated HCl (mL) = (1 N) × (36.46 g/mol) × (1.19 g/mL) / (37%) ≈ 31.7 mL

2.

Measure the required volume of concentrated HCl

Using a measuring cylinder, carefully measure out approximately 31.7 mL of concentrated HCl. Be cautious, as concentrated HCl is highly corrosive and can cause severe burns.

3.

Transfer the concentrated HCl to a beaker

Pour the measured volume of concentrated HCl into a beaker. Always add the acid to water, not the other way around, to minimize the risk of splashing.

4.

Add distilled water to the beaker

Gradually add distilled water to the beaker while stirring the solution. Continue adding water until the total volume reaches 1 liter.

5.

Stir the solution

Stir the solution thoroughly to ensure that the concentrated HCl is completely diluted and mixed with the water.

6.

Finalize the solution

Once the solution is well-mixed, transfer it to a clean, labeled bottle. Store the 1N HCl solution in a cool, dry place, away from direct sunlight and incompatible materials.

By following these steps, you can successfully prepare a 1N HCl solution from concentrated HCl. Always remember to handle concentrated acids with extreme caution and follow proper safety protocols.