Question

Will a precipitate form if 20 mL of `1 x 10^-7` M `AgNO_3` is mixed with 20 mL of `2 x 10^9` M `NaCl` at 25°C? For `AgCl`, `K_(sp) = 1.8 x 10^-10`

Answer 1

`"Non..........."`

Explanation:

We assess the equilibrium reaction:

`Ag^(+) + Cl^(-) rightleftharpoons AgCl(s)darr`, `K_"sp"=1.8xx10^-10`

Now `K_"sp"=[Ag^+][NO_3^-]`, and initially, we have the following concentrations:

`[Ag^+]=(20xx10^-3Lxx1.0xx10^-7*mol*L^-1)/(40xx10^-3*L)=5xx10^-8*mol*L^-1`

`[Cl^-]=(20xx10^-3Lxx2.0xx10^-9*mol*L^-1)/(40xx10^-3*L)=1xx10^-9*mol*L^-1`

Note that I assume you meant that `[NaCl]=2xx10^-9*mol*L^-1`, the given concentration is unreasonably high.

Now the ion product, `Q_"rxn"=[Ag^+][Cl^-]=5xx10^-8xx1xx10^-9=5xx10^-17`.

And since `Q_"rxn"` `<` `K_"sp"` precipitation of `AgCl` should not occur.