Question

The US Environmental Protection Agency (EPA) places limits on the quantities of toxic
substances that may be discharged into the sewer system. Limits have been established for a
variety of substances, including hexavalent chromium, which is limited to 0.50 mg/L. If an
industry is discharging hexavalent chromium as potassium dichromate (KC01), what is the
maximum permissible molarity of that substance?

Answer 1

Molecular weight of potassium dichromate is 294 g/mol which can also be written as 294 mg/m-mol

Max permissible limit is 0.50mg/L

No. of moles in 0.50mg potassium dichromate is 0.50/294 = 0.0017 m-mol

Therefore maximum permissible molarity is 1.7x10^-3 mM