Question

The Ksp for silver chromate (Ag2CrO4) is 1.1x10-12. Using the same initial set up of 10mL of 1M silver nitrate is combined with 25mL of 0.1M sodium chromate, what is the reaction quotient (Q) of the silver chromate? (Is a precipitate going to form?)

Answer 1

The solubility equation is given as follows

Ag2CrO4 <-> 2Ag+ + CrO4-2

Ksp = [Ag+]^2[CrO4-2]

No that Ksp is the actual values in equilibrium

We get a reference value of "Q" which is the calculated quotient

if Q > Ksp, there will be precipitation

Q = [Ag+]^2[CrO4-2]

Total V = V1+V2 = 10+25 = 35 mL

[AgNO3] = M1*V1/(VT) = 10*1/35 = 0.28571 M

[Na2CrO4] = M2*V2/VT = 25*0.1/35 = 0.07142 M

Now,

[Ag+] = [AgNO3] =0.28571

[Na2CrO4] = [CrO4-2] =  = 0.07142 M

Q = (0.28571 ^2)(0.07142 )

Q = 0.0058300

Q = 5.8*10^-3

Since

Q >>> Ksp

expect solid formation, that is, precipitation