How to Prepare a 2 M HCl Working Solution from a 10 M HCl Stock Solution

When dealing with the preparation of solutions, accuracy and safety are paramount. In this guide, we will explore how to prepare a 2 M HCl (Hydrochloric Acid) working solution from a 10 M HCl stock solution. This process involves understanding basic principles of solution dilution and applying them correctly to achieve the desired concentration.

Understanding the Stock Solution

A stock solution is a concentrated solution that is subsequently diluted to prepare a working solution. In this case, we have a 10 M HCl solution in a 100 mL volumetric flask. This means that there is 10 mL of HCl in the 100 mL solution. To prepare a 2 M HCl working solution, we need to calculate the volumes required for both HCl and water.

Step-by-Step Procedure

Using the principle of dilution, C1V1 C2V2, where C1 is the concentration of the stock solution (10 M), V1 is the volume of stock solution required, C2 is the concentration of the working solution (2 M), and V2 is the volume of the working solution (which we need to prepare).

Rearranging the formula to solve for V1:

C1V1 C2V2 > V1 (C2V2) / C1

Substituting the given values:

V1 (2 M times; V2) / 10 M

Assuming V2 (volume of working solution) is 500 mL, we substitute it:

V1 (2 M times; 500 mL) / 10 M 100 mL

So, we need 100 mL of the 10 M HCl stock solution and 400 mL of water to make 500 mL of 2 M HCl.

Practical Application and Safety Considerations

Always add acid to water and never the reverse to prevent splashing and ensure safety. Here's the detailed procedure:

Add one volume of the 10 M HCl stock solution (100 mL) to four volumes of water (400 mL). Swirl the solution occasionally to ensure proper mixing.

Transfer the 100 mL of the 10 M HCl solution into a 500 mL volumetric flask. Slowly add 400 mL of water to the flask, ensuring that you do not exceed the 500 mL mark. Swirl the solution gently to mix it thoroughly. Continue adding water until the meniscus reaches the 500 mL mark on the neck of the flask. Close the flask tightly and invert it several times to ensure uniform mixing.

Conclusion

Preparing a 2 M HCl working solution from a 10 M stock solution is straightforward once you understand the principles of dilution. Always prioritize safety by adding acid to water and following the detailed procedure provided. This method ensures the accuracy and consistency of your solution, which is crucial for many scientific and industrial applications.