What did you observe after the addition of dilute HCl to the saturated lead chloride solution? Explain observations using relevant chemical reaction.

I observed that a white precipitate was formed.

Not sure how to explain why it formed

You had a saturated solution of PbCl2 which means that (Pb^+)(Cl^-)^2 was just equal to Ksp.

When you added dilute HCl, you increased the (Cl^-) [the common ion effect] and this DECREASED the solubility of PbCl2; therefore, some of the PbCl2 pptd and that's what you saw.
PbCl2 ==> Pb^2+ + 2Cl^-

(Pb^2+)(Cl^-)2 = Ksp.
So note that if (Cl^-) is added to the above equation, the Cl^- is increased, Le Chatelier's principle tells you that will force the equilibrium to the left and that DECREASES solubility which means some of the PbCl2 from the saturated solution must come out of solution. You observed that as a ppt.

Thank you!

The formation of a white precipitate when dilute hydrochloric acid (HCl) is added to a saturated lead chloride (PbCl2) solution can be explained by the following chemical reaction:

PbCl2 + 2HCl -> PbCl4 + 2H2O

In this reaction, the hydrochloric acid reacts with lead chloride to form lead tetrachloride (PbCl4) and water (H2O). Lead tetrachloride is a white solid, which appears as a precipitate when it is formed in the solution.

The reason for the formation of the white precipitate is due to the limited solubility of lead chloride in water. When hydrochloric acid is added, it provides chloride ions (Cl-) which react with the lead ions (Pb2+) from the lead chloride. This reaction reduces the concentration of lead ions in the solution and exceeds its solubility limit, causing the lead tetrachloride precipitate to form.

The precipitate is white because lead tetrachloride is a white solid. The formation of the white precipitate confirms the presence of lead ions in the solution and indicates that the reaction between lead chloride and hydrochloric acid has taken place.

To explain the formation of the white precipitate when dilute hydrochloric acid (HCl) is added to a saturated lead chloride (PbCl2) solution, we need to understand a few relevant chemical reactions.

When HCl is added to the lead chloride solution, a double displacement reaction occurs between the chloride ions (Cl-) from both compounds. The chemical equation for this reaction can be represented as:

PbCl2 + 2HCl -> PbCl2(s) + 2H+(aq) + 2Cl-(aq)

In this equation, PbCl2 represents the lead chloride compound, which is initially in aqueous form. HCl represents the hydrochloric acid, which is also in aqueous form. The arrow indicates the reaction taking place, and (s), (aq) represent solid and aqueous states, respectively.

Here's a step-by-step explanation of the reaction:

1. The chloride ions (Cl-) from both the lead chloride compound (PbCl2) and hydrochloric acid (HCl) are involved in the reaction.

2. The chloride ions from HCl displace or replace the chloride ions already present in the lead chloride solution.

3. As a result of the reaction, lead chloride precipitates out of the solution as a solid (PbCl2(s)).

The white precipitate formed is the solid lead chloride, which is no longer soluble in the solution. This is due to the relatively low solubility of lead chloride in water.

In summary, the addition of dilute hydrochloric acid to a saturated lead chloride solution leads to a white precipitate formed due to a double displacement reaction, where the chloride ions from HCl replace the chloride ions in the lead chloride solution, resulting in the formation of solid lead chloride.