Question

. Assume you have 200 mL of a riboflavin stock solution at a concentration of 50 mg/L and you want to dilute this to a final concentration of 30 ng/L.

(a) If you wanted a final total volume of **100
mL**, how much of your original stock solution are you going
to have to use? Show your work.

Answer #1

We have 200 mL of riboflovin with concentration of 50 mg/L

So i have 50 mg/L * 200 mL = **10 mg of riboflavin in 200
mL**

I need the final concentration of the 30 mg/L with volume of 100 mL

so the amount of riboflaving to be present = 30 mg/L * 100 mL =
**3 mg riboflavin**

**so i need 3 mg of riboflavin**

**10 mg of riboflavin is present in 200 mL**

**3 mg will be present in (3 mg * 200 mL)/10 mg = 60
mL**

**so i need 60 mL of the initial stock of riboflaving to
prepare 100 mL of riboflavin with a concentration of 30
mg/L**

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