You work for a large urban water company. A pipe has broken in a recycling plant

Question

You work for a large urban water company. A pipe has broken in a recycling plant and flooded the inside of the building. The company recycles batteries, fluorescent lights, and electronic equipment, so hazardous levels of silver, mercury and lead ions may have contaminated the floodwaters.

You are the only person in the department who has had college chemistry, so your supervisor has asked you to devise a procedure to test the waters for the presence of AG^+, Hg^2+, and/or Pb^2+ ions. This procedure is to be written in a step-wise fashion, so that a technician in the water qualify laboratory will be able to follow it. Also an explanation of each step should be given. Why would you do that? What does it accomplish? How does it accomplish the separation and/or identification of a particular ion? Samples of the food waters have already been collected and are already waiting in the laboratory for you. You will follow your procedure to test a sample for yourself during your scheduled lab time.

Assuming that the water is contaminated, devise a method for disposing of the contaminated water without contaminating the environment, but allowing the recycling plant to resume operations as soon as possible.

Explanation / Answer

all give 3 cations gets precipitated when treated with HCl

AgCl, Hg2Cl2 , PbCl2

now these precipitae is treated with aq NH3

then AgCl gets dissolved , thus Ag+ can be identified here

AgCl + AqNH3 ------> [Ag(NH3)2]2+(aq) + Cl-(aq)

if precipate is not dissolved then either Hg2+ , Pb2+ are present

now add hot water and heat PbCl2 dissolves in hot water , thus it can be identified here

PbCl2 ----> Pb2+(aq) + 2Cl-(aq),

if precipate is not dissolved in hot water it is Hg2Cl2 , hence Hg2+ can be identified.

All these cations can be removed as their chlorides (ppt)

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