Question

In the St. Louis River, fish tissues have been found to exceed the 0.5 mg Hg per kg tissue criterion set up to protect food webs (higher trophic level fish, birds, etc). What is this level in ppm? What is the molarity of Na+ in an aqueous solution containing 333 ppb of NaNO3?

Answer 1

Concentration of Hg = 0.5 ppm

Concentration of Na⁺ = 3.92 × 10⁻⁶ M

Step-by-step explanation:

The level of Hg is 0.5 mg Hg per kg tissue. What is this level in ppm?

Depending on the context, ppm may refer to mg/kg (ppm in mass) or mg/L(ppm in volume). In this case, we assume it is ppm in mass. Since the level of Hg is 0.5 mg/kg, it is the same as 0.5 ppm.

What is the molarity of Na+ in an aqueous solution containing 333 ppb of NaNO₃?

Depending on the context, ppm may refer to μg/kg (ppb in mass) or μg/L(ppb in volume). In this case, we assume it is ppb in mass. We can find the molarity of Na⁺ (moles of Na⁺ per liter of solution) using proportions.

`333ppbNaNO_(3)=(333\mu gNaNO_(3) )/(1L) .(10^(-6)gNaNO_(3) )/(1 \mu gNaNO_(3) ) .(23.0gNa^(+) )/(85.0gNaNO_(3)) .(1molNa^(+))/(23.0gNa^(+) ) =3.92 * 10^(-6) M`