How do we describe the solution behaviour of #PbCl_2(aq)#?

Question

Jeremiah Adams · Accepted Answer

Lead(II) chloride is very insoluble in aqueous solution. The filtrate is saturated with respect to #Pb^(2+)#.

A solution is said to be saturated when the solute concentration is the same as what would be in equilibrium with an undissolvable solute: #PbCl_2(s) rightleftharpoons PbCl_2(aq)#, i.e. #PbCl_2(s) rightleftharpoons Pb^(2+) + 2Cl^-# A temperature is typically specified because a hot solution can typically hold more solute than a cold one. The solution that lies atop undissolved solute is called the supernatant solution, and it is said to be saturated with respect to lead chloride. We can express the reaction in terms of an equilibrium constant for any equilibrium: #K_(sp) = [Pb^(2+)][Cl^-]^2# #=# #"A small number"#. The subscript #"sp"# stands for solubility product. These are extensively tabulated for a range of sparingly soluble and insoluble salts; normally, laboratory temperature, #298# #K# is specified. So if #[Cl^-]# is artificially increased (by adding #Cl^-#), the ion product, #[Pb^(2+)][Cl^-]^2# will be momentarily GREATER than #K_(sp)#. In order to obey the #K_(sp)# expression, lead chloride will precipitate in order to reduce #[Pb^(2+)]# and #[Cl^-]#. I admit that I have been talking about nothing to the power of less for a while. The key definition is as follows: A solution is said to be saturated when the solute concentration is the same as what would be in equilibrium with an undissolved solute. A definition of a saturated solution as one in which the solvent holds all of the solute it can would be rejected by an examiner with good reason.

Kai Bowman · Answer

undefined PbCl2(aq) forms a saturated solution in water, meaning it reaches a maximum concentration where no more solute can dissolve. It dissociates partially into lead ions (Pb^2+) and chloride ions (Cl^-) in aqueous solution, following the equation: PbCl2(s) ⇌ Pb^2+(aq) + 2Cl^-(aq). However, it also forms a complex ion, PbCl4^2-, especially in concentrated solutions, contributing to its solubility. Overall, PbCl2 demonstrates limited solubility in water, with the extent of dissociation depending on factors such as temperature and presence of other ions.