Final answer:
To prepare a 250 mL solution with a molarity of 0.25M, you need to use 4.66 grams of KCl, calculated through the molarity formula and the molar mass of KCl.
Step-by-step explanation:
To find the grams of KCl required to prepare 250 mL of a 0.25M solution, we first need to convert the volume from milliliters to liters, as molarity is expressed in moles per liter. Since there are 1000 mL in a liter, 250 mL is equal to 0.250 liters. Using the formula:
Molarity (M) = moles of solute / liters of solution,
We can rearrange it to find the moles of solute:
moles of solute = Molarity (M) × liters of solution,
Substituting the given values:
moles of KCl = 0.25M × 0.250L = 0.0625 moles.
Next, we use the molar mass of KCl (74.55 g/mol) to find the mass:
mass of KCl = moles of KCl × molar mass of KCl
mass of KCl = 0.0625 moles × 74.55 g/mol = 4.659375 g
Therefore, you would need 4.66 grams of KCl to prepare 250 mL of a 0.25M KCl solution.