Question

analysis of a 100 ml water a sample finds 3.2x10^(-6) g of mercury. current state and federal maximum contaminant level (mcl) for mercury is 2 micrograms per liter. a.) what is the concentration in μg/l for mercury in this sample? complete the following equation to arrive at the number of μg/l in this sample: $\frac{3.2x10^{-6}g}{100ml} \times (\frac{1μg}{?g})(\frac{1ml}{?l}) =?\frac{μg}{l}$ b.) how many times over or under the mcl for mercury is this sample? $(\frac{?\frac{μg}{l}}{mcl}) =?$ 32 μg/l, 16 times over 320 μg/l, 6.4 times over 32 μg/l, 1.6 times over 3.2 μg/l, 1600 times over

Explanation:

Step1: Convert grams to micrograms

We know that $1\ g = 10^{6}\ \mu g$. So, for $3.2\times 10^{-6}\ g$ of mercury, the amount in micrograms is $3.2\times 10^{-6}\times10^{6}=3.2\ \mu g$. The volume of the sample is $100\ mL = 0.1\ L$.

Step2: Calculate the concentration in $\mu g/L$

The concentration $C$ of mercury in the sample is given by the formula $C=\frac{\text{mass in }\mu g}{\text{volume in }L}$. Substituting the values, we have $C = \frac{3.2\ \mu g}{0.1\ L}=32\ \mu g/L$.

Step3: Determine how many times over the MCL

The MCL for mercury is $2\ \mu g/L$. To find out how many times over the MCL the sample is, we calculate $\frac{32\ \mu g/L}{2\ \mu g/L}=16$.

Answer:

32 $\mu g/L$, 16 times over