A Homeowner in Boston Becomes Concerned That There May Be

Multiple Choice

A homeowner in Boston becomes concerned that there may be appreciable amounts of lead in her drinking water due to 150-year old water pipes in her house. Consequently, she takes a sample of her drinking water in to be analyzed. The laboratory technician, who is new on the job, has been told to analyze by precipitating the lead ion as the iodide (Ksp = 7.1 × 10^-9 for PbI2) by slowly adding small portions of 1.00 M NaI solution. If we assume that the concentration of lead in the solution is 1.00 mg/liter or approximately 4.8 × 10-6 M (this would be 1.0 part per million) is it possible to detect the lead in the drinking water by adding a total of no more than 10.0 mL of NaI solution to a 100 mL sample of drinking water? You must of course consider dilution effects. What is Q?

A) yes, Q = 4.0 × 10^-7
B) yes, Q = 3.6 × 10^-8
C) no, Q = 1.6 × 10^-13
D) no, Q = 3.6 × 10^-8
E) no, Q = 4.0 × 10^-7