Question

Pesticide concentrations in the portion of the Rhine River that flows between Germany and France averaged 0.55 mg/L of hexachlorobenzene (C6Cl6), 0.06 mg/L of dieldrin (C12H8Cl6O), and 1.02 mg/L of hexachlorocyclohexane (C6H6Cl6) between 1969 and 1975. Express these concentrations in millimoles per liter.

Answer 1

Explanation:

1) Concentration of hexachlorobenzene = 0.55 mg/L

1 mg = 0.001 g

$0.55 mg/L=0.55\times 0.001 g/L=0.00055 g/L$

Molar mass of hexachlorobenzene = 285 g/mol

Concentration of hexachlorobenzene in mol/L:

$=\frac{0.00055 g/L}{285g/mol}$

1 mole = 1000 milli moles

Concentration of hexachlorobenzene in millimoles per Liter:

$=\frac{0.00055 g/L}{285g}\times 1000 millimole$

$=0.001929 millimol/L$

2) Concentration of hexachlorobenzene = 0.06 mg/L

1 mg = 0.001 g

$0.06mg/L=0.06\times 0.001 g/L=0.00006 g/L$

Molar mass of dieldrin = 381 g/mol

Concentration of dieldrin  in mol/L:

$=\frac{0.00006 g/L}{381/mol}$

1 mole = 1000 milli moles

Concentration of dieldrin in millimoles per Liter:

$=\frac{0.00006 g/L}{381 g}\times 1000 millimole$

$=0.0001575 millimol/L$

3) Concentration of hexachlorocyclohexane = 1.02 mg/L

1 mg = 0.001 g

$1.02 mg/L=1.02\times 0.001 g/L=0.00102 g/L$

Molar mass of hexachlorocyclohexane = 291 g/mol

Concentration of hexachlorocyclohexane in mol/L:

$=\frac{0.00102 g/L}{291/mol}$

1 mole = 1000 milli moles

Concentration of hexachlorocyclohexane in millimoles per Liter:

$=\frac{0.00102 g/L}{291g}\times 1000 millimole$

$=0.003505 millimol/L$