A 2.5% KCl solution is prepared by dissolving enough of the salt to give 181.4 g of solution. What mass (g) of water is required?

To find the mass of water required, we'll use the fact that the mass percentage is the ratio of the mass of solute to the mass of the solution, and the mass of the solution is the sum of the masses of the solute and the solvent.

Let's start by assuming the mass of water required is "x" grams.

In this case, we know that the mass of the KCl solution is 181.4 grams. Since the KCl solution is 2.5% KCl, we can find the mass of KCl using the equation:

Mass of KCl = 2.5% × Mass of solution

To solve for the mass of KCl, we can rearrange the equation as follows:

Mass of KCl = (2.5/100) × 181.4 grams

Now, we can find the mass of water by subtracting the mass of KCl from the total mass of the solution:

Mass of water = Mass of solution - Mass of KCl

Substituting the given values:

Mass of water = 181.4 grams - (2.5/100) × 181.4 grams

Simplifying the equation:

Mass of water = 181.4 grams - 4.535 grams

Mass of water = 176.865 grams

Therefore, approximately 176.865 grams of water is required to prepare the 2.5% KCl solution.