Molarity - It is defined as number of moles of solute in the given solution.
Molarity = number of moles / Volume of solution
moles = mass / molecular weight
Molecular weight of KCl =( K-39) + (Cl -35.5) = 74.5 g/mole
Volume of soultion = 250 mL = 0.25L
Molarity = 0.5 M
Now ,
Molarity = number of moles / volume of solution
= Mass of KCl / molecular weight of KCl × Volume
0.5 = Mass of KCl / 74.5 × 0.25
Mass of KCl = 0.5 × 74.5 × 0.25 = 9.3125 grams
Hence the mass of KCl required is 9.3125 grams.
