Question

0.000333 g fluorescein (332.32 g/mol) is dissolved in 225 mL solution of ethanol. The density of ethanol is 0.785 g/mL.

What is the concentration of the solution in molarity (M)?

How many ppm?

I already know that the molarity is 4.45E-6. I just need help on trying to find the ppm please.

Answer 1

mass = volume x density for ethanol.
mass = 225 x 0.785 g/mL = 176.6 g EtOH.

ppm = g solute/10^6 g soln
g solute = 0.000333
g soln = 0.000333+176.6 = 176.6
0.000333/176.6 = 1.8 somethingE-6; therefore, this is 0.000333g solute/g soln. Multiply by 10^6 to find g/10^6 g = about 1.8 ppm. You can find a more accurate answer as I've estimated here and there.

Answer 2

Thank you very much!