Children under the age of six with more than 0.10 ppm of lead in their blood can suffer a reduction in I.Q. or have behavior problems. What is the molality of a solution which contains 0.10 ppm of lead?

Question

Quizplus · Accepted Answer

To convert parts per million (ppm) to molality (m), we need to use the following formula:

m = (mass of solute in moles) / (mass of solvent in kg)

Assuming the solvent is pure water, we can use the density of water (1 g/mL) to convert the mass of solvent (i.e., volume of solution) to kg.

The molar mass of Pb is approximately 207.2 g/mol. Therefore, to find the mass of Pb in 0.10 ppm of blood, we need to know the mass of blood. Let's assume a small child has a blood volume of about 1 L (1000 mL) and a density of 1.06 g/mL. This would give a mass of blood of 1060 g (1.06 kg).

Now, we can calculate the mass of Pb in 0.10 ppm of blood:

mass of Pb = (0.10 ppm) x (1 g / 10^6 ppm) x (1060 g) = 0.106 g

Finally, we can use the formula to calculate the molality:

m = (0.106 g / 207.2 g/mol) / 1 kg = 5.12 x 10^-8 mol/kg

This is closest to option B.

Children Under the Age of Six with More Than 0