posted by Norma on .
What formula do I use to calculate the mass of KCl that is required to make 625 mL of a 0.200 M solution?
Dr Robb the formula you gave me didn't give me the correct answer and I think I did it wrong it is asking for the answer in grams which should be 9.3 grams but I cant get that answer no matter how I work it. Help please
You just didn't use it correctly.
M = moles/L
moles = M x L = 0.200 M x 0.625 L = 0.125 moles.
grams = moles x molar mass
g = 0.125 x 74.55 = 9.3187 grams which rounds to 9.32 grams KCl to three significant figures (which is what you are allowed). .
thank you so much Dr Bob I couldn't figure it out at all.