how much sodium chloride must be added to 100 mL of water so that its concentration is 20 parts per million assume that the density of water is 1.00g/ml
Part per million is unit that equal to mg/kg of water or simply [tex] 10^{-6} [/tex] . In this case, you asked how much NaCl needed and know the volume of water(100mL), concentration(20ppm or 20 mg/kg) and water density. Then, the equation would be
concentration = NaCl weight/ water weight 20 x [tex] 10^{-6} [/tex] mg= NaCl weight/ (100ml x 1g/ml) NaCl weight= 20x [tex] 10^{-6} [/tex] mg/kg x 100g NaCl weight= 2000 x [tex] 10^{-6} [/tex] g NaCl weight= 2x [tex] 10^{-3} [/tex] g = 2mg
