Answer:
concentration in ppm of DDT = 0.011 ppm
Explanation:
since ppm of DDT =mg of DDT /Kg of solution ( or μg of DDT /g of solution) , then
concentration in ppm of DDT = 4.21 × 10⁻⁷ kg * 10⁶ mg/kg / ( 1.00 g/mL * 3.7 L * 1000 ml/L * 1 kg/1000gr) = 0.011 ppm
then
concentration in ppm of DDT = 0.011 ppm
