A chemical is placed in a beaker containing 20 g of soil and 500 mL of water. At equilibrium, the chemical is found in the soil ast a concentration of 100 mg. kg-1 of soil. The equilibrium concentration of this same chemical in the water is 250 What is the partition coefficient for this chemical on this soil? Answer: 400 mg kg-1/mg L-1

Kd = 400 (mg/kg) / (mg/L)

Explanation:

Assume that the units for the concentration of the chemical in water is μg/L

Convert units of concentration of chemical in water to mg/L

Cw = 250 μg/L

Here, the concentration of chemical in water is Cw

1 mg = 11000 μg

Cw = 250 x 10⁻³mg/L

Calculate the partition coefficient for the chemical in soil as follows

Kd = Cs/Cw

Here, the partition coefficient is Kd, the concentration on the soil at equilibrium is Cs and the concentration of chemical in water at equilibrium is Cw.

Substitute 250 x 10⁻³ mg/L for Cw and 1000 mg/kg for Cs

Kd = 100 (mg/kg)) / (250 x 10⁻³) (mg/L)

Kd = 400 (mg/kg) / (mg/L)