. The level of mercury in a stream was suspected to be above the minimum considered safe (1 part per billion by weight). And analysis indicated that the concentration was 0.68 parts per billion. Assume a density of 1.0 g/mL and calculate the molarity of mercury in the stream.

3.39x10⁻⁹ M

Explanation:

Let's assume we have 1 mL of the stream. With a density of 1.0 g/mL, we would have 1 g of the stream.

Now we calculate the mass of mercury present in 1 g of the stream, using its given concentration (0.68 ppb):

Now we convert that mass into moles, using mercury's atomic mass:

Finally we calculate the molarity of mercury, as we know that there are 3.39x10⁻¹² Hg moles in 1 mL of the stream:

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