Lead nitrate is an inorganic compound having the following formula: Pb (NO3) 2. In the usual state, it is a white powder or colorless crystals. This substance is highly soluble in water.
Physical properties
1. It dissolves well with heat absorption in H2O (water), poorly in acetone, as well as in methyl and ethyl alcohols.
2. Forms diamagnetic colorless crystals with a density of 4.530 g / centimeter³. Each Pb atom (lead) is surrounded by twelve O (oxygen) atoms. The Pb-O bond length is 0.281 nm, and NO is 0.127 nm. Represents a cubic syngony. Belongs to the space group Pa3. In addition to the cubic variety, a monoclinic form was also obtained, which, even when heated, is poorly soluble in H2O (water).
3. Lead, melting point is 600.65 K.
How to get lead nitrate
This substance is not found in nature. Therefore, people have created some methods (industrial and laboratory), which boil down to the dissolution of lead (Pb), its hydroxide or oxide in dilute nitric acid. Reactions:
3Pb (lead) + 8HNO3 (nitric acid) = 3Pb (NO3) 2 (lead nitrate) + 2NO (nitrogen oxide, liberated as a gas) + 4H2O (water);
PbO (lead oxide) + 2HNO3 (nitric acid) = Pb (NO3) 2 (lead nitrate) + H2O (water);
Pb (OH) 2 (lead hydroxide) + 2HNO3 (nitric acid) = Pb (NO3) 2 (lead dinitrate) + 3H2O (water).
In order to suppress hydrolysis and reduce the solubility of lead dinitrate, nitric acid must be taken in excess.
Lead dinitrate is also obtained as a by-product in the treatment of waste with nitric acid, for example, in the treatment of bismuth-lead waste in factories. This compound is subsequently used for cyanidation of gold.
What are the chemical properties of lead nitrate?
1. In an aqueous solution, lead nitrate dissociates into nitrate anions and lead cations. This is what the reaction looks like:
Pb (NO3) 2 (lead dinitrate) = Pb2 + (lead cation) + 2NO3- (nitric oxide anion)
The solution of lead dinitrate is hydrolyzed. With an excessive amount of NO3-, nitrate complexes are formed: [Pb (NO3) 6] 3−, [Pb (NO3) 4] 2−, and [Pb (NO3) 3] -. If you increase the pH of the solution, the result is hydronitrate Pb (OH) x (NO3) y variable composition. Some of them are isolated in the solid state.
2. Since lead dinitrate is a soluble compound, the following exchange reactions can be obtained:
2HCl (hydrochloric acid) + Pb (NO3) 2 = PbCl2 (lead chloride, precipitated) + 2HNO3 (nitric acid);
H2SO4 (sulfuric acid) + Pb (NO3) 2 = PbSO4 (lead sulfate, precipitated) + 2HNO3 (nitric acid);
Pb (NO3) 2 (lead nitrate) + 2NaOH (sodium hydroxide) = Pb (OH) 2 (lead hydroxide, precipitates) + 2NaNO3 (sodium nitrate);
Pb (NO3) 2 + 2NaN3 (sodium azide) = Pb (N3) 2 (lead azide, precipitated) + 2NaNO3 (sodium nitrate).
Any chemical compound containing a lead cation (Pb + 2) will react with a solution in which there is an iodide anion. In this case, a yellow-orange precipitate forms (Pbl2, lead iodide). This reaction looks like this:
Pb2 + + 2l- = Pbl2 (precipitate)
The same exchange reaction occurs in the solid phase. For instance:
Pb (NO3) 2 + 2Kl (potassium) = Pbl2 (precipitated) + 2KNO3 (potassium nitrate)
The use of lead nitrate
- It is used as an initial raw material for the production of most other Pb compounds (lead);
- as an inhibitor of nylon polymers and some other polyesters, in the role of a zoocide, in photothermographic paper coatings;
- since lead nitrate is a rather dangerous compound, other compounds are currently used in the industrial field. For example, in the manufacture of paints, matches and fireworks, lead compounds were completely abandoned.
- in laboratory practice, lead nitrate is used as a good and convenient source of diazot tetraoxide;
- More recently, in very limited quantities, this chemical compound is used in the cyanidation of gold.
- in organic chemistry, Pb (NO3) 2 is used as an oxidizing agent to produce isothiocyanates from dithiocarbamates. Due to its high toxicity, it is used less and less.
Security
Lead nitrate is classified as category 2A (probably a carcinogen in humans). Inhalation of its toxic fumes or ingestion, as well as contact with the skin or mucous membrane, is not allowed. Lead dinitrate should be constantly monitored. Poisoning with this chemical compound leads to poisoning, gliomas and cancer of the kidneys, brain and lungs.