What mass of KCl (MM = 74.55 g/mol) is required to make 550 mL of a 0.250 M solution?

How many mols do you want? That's M x L = ?

Then mols = grams/molar mass. You know mols and molar mass, solve for grams.

To answer this question, we need to use the formula:

Molarity = moles of solute / volume of solution (in liters)

First, we need to convert the given volume from milliliters (mL) to liters (L):

550 mL = 550/1000 L = 0.55 L

Now, we can rearrange the formula to solve for moles of solute:

moles of solute = Molarity * volume of solution

moles of solute = 0.250 M * 0.55 L = 0.1375 moles

Finally, we can calculate the mass using the molar mass (MM) of KCl:

mass = moles of solute * MM

mass = 0.1375 moles * 74.55 g/mol = 10.21125 g

Therefore, 10.21125 grams of KCl are required to make 550 mL of a 0.250 M solution.