Question

0.000333 g fluorescein is dissolved in 225 mL solution of ethanol. The molar mass of fluorescein is 332.32 g/mol and the density of ethanol is 0.785 g/mL. What is the concentration of the solution in molarity? Number M fluorescein What is the concentration of the solution in ppm? Number ppm fluorescein

Answer 1

The concentration of the solution in molarity is 4.45*10^-6M

The concentration of the solution in ppm is 1.88

Step-by-step explanation:

First of all we have to find out how many mols are 0.000333 g of fluorescein. We would use the molar mass of it.

So 0.000333g / 332.32 g/m = 1.002*10^-6 moles

This moles are in 225 ml of ethanol. Molarity as you should know are moles of solute in 1 L of solution (either 1000 ml)

225 ml ______ 1.002*10^-6 moles

1000 ml _____ x x = (1000*1.002*10^-6) /225 = 4.45*10^-6M

The ppm means mg of solute that are in 1 kg of solvent.

Let's consider density of ethanol to get the mass.

d = m/v

0.785 g/ml = m/225 ml

0.785 g/ml . 225 ml = m

176.625 g = m

Now, let's convert

0.000333 g *1000 = 0.333 mg

176.625g / 1000 = 0.176625 kg

0.333/0.176625 = 1.88 ppm