Question

The Ksp expression for the system PbCl2(s) Pb+2(aq) + 2 Cl-(aq) is:

Answer 1

The solubility expression for this system would be the mathematical products of the chemical products, divided by the mathematical products of the chemical reactants, with each component being raised to the power denoted by their respective coefficients (gross!). The only exception is that components present in the solid state are excluded from this calculation. So:

Ksp=(Cl-)^2(Pb2+)

Notice that Cl is raised to the power of two, due to the coefficient present in the balanced reaction, and that PbCl2 is excluded from the calculation due to it’s state.

Answer 2

`ksp = [Cl^(-1) ]^2 * [Pb^+1]`

Step-by-step explanation:

The ksp is the constant of the product of solubility (it tells us that so much substance is going to dissolve and that this is constant), it is like the constants of equilibrium (equation 1). This is the concentration of the products (C and D) divided into the concentration of the reagents (A and B) raised to their stoichiometric coefficients (a, b, c, d).

Reaction 1.
`aA  + bB` ⇒
`cC + dD`

Equation 1.
`K = ([C]^c* [D]^d)/([A]^a*[B]^b)`

In this case the reagents are a salt in solid state - PbCl2(S) - this will not be taken into account in the expression of Ksp (neither liquids, nor solids are taken into account) only the substances in gaseous state (g) or in dissolution (aq). In the products there are two moles of ions
`Cl^(-1)` (aq) therefore its expression in ksp is
`[Cl^(-1)]^(2)` and of ions
`Pb^(+1)` there is a mole and in the expression will be
`[Pb^(+1)]`. According to the above the expression of ksp is:

`ksp = [Cl^(-1) ]^2 * [Pb^+1]`