What is the concentration of a solution made by diluting 85 mL of 6.0 mg/L free chlorine to a final volume of 750 mL?

you are diluting it 750/85 times, so new concenetraion is 6.0mg/l * 85/750

To find the concentration of the diluted solution, you need to use the formula:

C1V1 = C2V2

Where:
C1 = initial concentration of the solution (in mg/L)
V1 = initial volume of the solution (in mL)
C2 = final concentration of the solution (in mg/L)
V2 = final volume of the solution (in mL)

In this case, you have:
C1 = 6.0 mg/L (initial concentration)
V1 = 85 mL (initial volume)
C2 = ? (final concentration, what we are trying to find)
V2 = 750 mL (final volume)

Substituting the given values into the formula, we have:
6.0 mg/L * 85 mL = C2 * 750 mL

Now, we can solve for C2:

C2 = (6.0 mg/L * 85 mL) / 750 mL

C2 ≈ 0.68 mg/L

Therefore, the concentration of the solution made by diluting 85 mL of 6.0 mg/L free chlorine to a final volume of 750 mL is approximately 0.68 mg/L.