Understanding HCl Concentration: 36 w/w HCl Solution

Hydrochloric acid (HCl) is a strong mineral acid that is widely used in various industrial processes and chemical experiments. One common specification for HCl is its weight per weight (w/w) concentration, such as 36 w/w, meaning that 36 grams of HCl are present in every 100 grams of the solution.

Concentration Calculation: From the Original to the Final Solution

The original concentration of a 36 w/w HCl solution can be determined using the formula:

Co (Pxd) / M

Here, Co is the original concentration in moles per deciliter (mol/dm3), P is the percentage of HCl, d is the density of HCl, and M is the molar mass of HCl.

Step-by-Step Calculation of the Original Concentration

For a 36 w/w HCl solution:

P (HCl percentage) 36% d (density of HCl) 1.2 g/cm3 M (molar mass of HCl) 36.5 g/mol

Substituting these values into the formula:

Co (36% x 1.2) / 36.5 11.8 mol/dm3

This means the original concentration of the 36 w/w HCl solution is 11.8 mol/dm3.

Dilution Calculation: Determining the Final Concentration

Now, let's consider a scenario where we take 7 cm3 of this concentrated HCl solution and dilute it to make 1 dm3 of the final solution. To calculate the final concentration, we use the dilution formula:

Concentrationinitial x Volumeinitial Concentrationfinal x Volumefinal

Applying the Dilution Formula

Given:

Initial Concentration (Co) 11.8 mol/dm3 Initial Volume (Vi) 7 cm3 Final Volume (Vf) 1 dm3 1000 cm3

The formula becomes:

11.8 mol/dm3 x 7 cm3 Concentrationfinal x 1000 cm3

Although the units are different (mol/dm3 and cm3), we can still solve for the final concentration in mol/dm3 as follows:

Concentrationfinal (11.8 mol/dm3 x 7 cm3) / 1000 cm3 0.0826 mol/dm3 ≈ 0.08 M

This means the final concentration of the solution after diluting 7 cm3 of the original solution to 1 dm3 is approximately 0.08 M.

Summary and Application

In summary, the original concentration of a 36 w/w HCl solution can be calculated to be 11.8 mol/dm3. When 7 cm3 of this solution is diluted to make 1 dm3 of the final solution, the concentration of the final solution is approximately 0.08 M.

This calculation is crucial for any scenario where HCl is used in laboratory settings or industrial processes, ensuring accurate measurements and safe handling.

Keywords: HCl, concentration, dilution calculation