COOP 1100 Lecture Notes - Lecture 5: Markham, Ontario, Biomonitoring, Caravel

Exam

for water quality management in environmental engineering

A common way of removing Cr³⁺ from solution is precipitation of Cr(OH)₃(s). An environmental engineer tells you that adjusting the pH to 8.5 will decrease the total soluble Cr(III) to below 1 mg/L. Is this true? In other words, is the solubility of Cr(III) in the presence of Cr(OH)₃(s) at a pH of 8.5 less than 1 mg/L? the pK_spof Cr(OH)₃(s) is 30.22.

Note: This question is in 5th edition of Chemistry for Environmental Engineering and Science. Chapter 4, Question 86.

1.An environmental monitoring detector system gives a read out of 5,316 counts in one minute for a 1 Liter water sample. The overall efficiency (geometry & intrinsic) of the counting system is 8 %. What is the activity of the sample in Bq?