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? A)4.8 $\times$ 10^-10 m B)4.8 $\times$ 10^-7 m C)4.8 $\times$ 10^-4 m D)4.8 $\times$ 10^-1 m E)None of these choices is correct.

Question

Quizplus · Accepted Answer

To calculate the molality of a solution, we need to find the number of moles of solute per kilogram of solvent. 
0.10 ppm means 0.10 parts of lead per million parts of solution. 
So, for every 1 million parts of solution, we have 0.10 parts of lead. 
Converting parts to grams, we have 0.10 g of lead in 1 million g of solution. 
This can be simplified to 0.10 g of lead in 1 kg of solution. 
So, the molality would be:
molality = moles of solute/kg of solvent
Since the molar mass of lead is 207.2 g/mol, we can calculate the number of moles of lead in 0.10 g:
moles of lead = 0.10 g / 207.2 g/mol = 0.000482 moles
So, the molality would be:
molality = 0.000482 moles / 1000 g = 4.82 x 10^-7 mol/g
This can be simplified to:
molality = 4.82 x 10^-4 mol/kg
Using scientific notation, we can write this as:
molality = 4.82 x 10^-4 m
Rounding this to one significant figure, we get:
molality = 5 x 10^-4 m
This is equivalent to 4.8 x 10^-7 m, which matches choice B.

Children Under the Age of Six with More Than 0 ×\times×

Children Under the Age of Six with More Than 0 $\times$