Question

The pesticide DDT (C14H9Cl5) was banned in the United States in 1972 because of dire environmental impacts. Just prior to its being banned, analyses of groundwater samples in Pennsylvania between 1969 and 1971 yielded the following results: Location sample size mass of DDT orchard 250.0 mL 0.030 mg Express these data in units of millimoles (mmol) of DDT per liter (L).

Answer 1

Answer:

Concentration of DDT in milli moles per Liters : $3.385\times 10^{-4} mmol/L$.

Explanation:

Mass of DDT in sample = 0.030 mg = 0.030 × 0.001 g = 0.00003 g

1 mg = 0.001 g

Molar mass of DDT = 354.5 g/mol

Moles of DDT sample = $\frac{0.00003 g}{354.5 g/mol}=8.463\times 10^{-8} mol$

1 mol = 1000 milli mol

$8.463\times 10^{-8} mol=8.463\times 10^{-8}\times 1000 mmol$

$=8.463\times 10^{-5} mmol$

Volume of the sample = 250.0 mL = 0.250 L (1 mL=0.001 L)

Concentration of DDT in milli moles per Liters :

$\frac{8.463\times 10^{-5} mmol}{0.250 L}=3.385\times 10^{-4} mmol/L$