Synthesis of Lead (II) Nitrate

Lead (II) nitrate is one of the few soluble lead compounds, thus is one of the few sources of lead (II) ions. Lead (II) nitrate is a clear, colorless ionic solid.

Since my lab is currently lacking nitric acid, lead (II) nitrate must be prepared by other methods. A possible route to lead (II) nitrate is a single replacement reaction between lead and the salt of a less reactive metal. First copper (II) nitrate must be prepared.

CuSO4 + 2 KNO3 ---> Cu(NO3)2 + K2SO4

Cu(NO3)2 + Pb ---> Pb(NO3)2 + Cu

Warnings:
Lead compounds are highly toxic. Lead will remain in a biological system for decades, doing damage. All lead compounds should be disposed of at your local hazardous waste disposal facility. Gloves and goggles were worn at all times during this experiment.
Copper compounds are moderately toxic.

Materials:
Potassium nitrate (Stump remover)
Copper (II) sulfate (Root killer for drains)
Lead metal (Lead fishing sinker)

July 27, 2005
59.3g potassium nitrate, 70g copper (II) sulfate and 200mL distilled water was added to a 300mL beaker. This is a slight excess of copper (II) sulfate so there is no potassium nitrate impurity since lead (II) sulfate will precipitate and copper will plate out. Immediately there was a precipitate, probably due to the low solubility of potassium sulfate. The beaker became slightly cool to the touch. The beaker was then heated on an hot plate and stirred until all of the reactants dissolved. When the beaker was cooled potassium sulfate began to precipitate again, this was allowed to continue until the beaker reached room temperature. The solution was decanted and filtered. 100mL of the solution was transferred to a beaker, the rest was transferred to a round bottom flask. A piece of lead metal was immersed in the solution. Very slight bubbling was observed. White fuzzy lead (II) sulfate soon appeared on the surface of the lead. This reaction was allowed to continue for several days until the solution turned colorless (No blue from copper ions).

Several days later the white fuzz was now covering the lead and the bottom of the beaker like moss. Copper formations had grown on the lead as well, which were covered in a blue dust. Water was added to replenish the water lost by evaporation. The solution was decanted and filtered and transferred to a flask. A few mL of the lead (II) nitrate solution was placed in a test tube and a few drops of weak ammonia solution was added. No noticeable change occurred but when the test tube was cleaned a white deposit was left behind on the glass. The lead contaminated glassware was cleaned thoroughly with a weak ammonia solution to precipitate the lead. All liquids used to clean the glassware were evaporated and the solids stored for safe disposal.

Unanswered Questions:

What is the blue dust and why did it form? Is it Cu(OH)₂?

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