How many grams of KNO3 are needed to make 450 mL of a solution that is to contain 5.50 mg/mL of potassium ion?

Question

Calculate the molarity of the solution.

______g
______M

i honestly don't know where to start, but i know that M=mol/L will be involved somewhere...

Please help...

Answer 1

You want 5.50 mg/mL and you want 450 mL. So mg needed = 5.50 mg/mL x 450 = ??mg
Convert that to grams. Then convert that many g K^+ to KNO3.
g KNO3 = g K^+ needed x (molar mass KNO3/atomic mass K^+) = ??

For M, convert grams KNO3 to moles. moles = grams/molar mass, then M = moles/L.