Understanding the Problem

* We have a concentrated solution of NaCl (0.91%) and need to dilute it to make a less concentrated solution (0.45%).

* We want to end up with 100 ml of the diluted solution.

Using the Dilution Formula

The dilution formula helps us calculate the volume needed from a concentrated solution to make a desired diluted solution. The formula is:

C₁V₁ = C₂V₂

where:

* C₁ = Concentration of the concentrated solution

* V₁ = Volume of the concentrated solution (what we need to find)

* C₂ = Concentration of the diluted solution

* V₂ = Volume of the diluted solution

Applying the Formula

1. Convert percentages to decimal form:

* 0.91% = 0.0091

* 0.45% = 0.0045

2. Plug the values into the formula:

* 0.0091 * V₁ = 0.0045 * 100 ml

3. Solve for V₁:

* V₁ = (0.0045 * 100 ml) / 0.0091

* V₁ ≈ 49.5 ml

Answer:

You would need approximately 49.5 ml of the 0.91% NaCl solution to prepare 100 ml of 0.45% NaCl solution.