Which of the equations below is correct for the following Ksp expression? Ksp = [Cd2+][OH-]2 Select one or more:

A. Cd2(OH)2(s) <---> 2Cd2+(aq) + 2OH2-(aq)
B. Cd(OH)3(s) <---> Cd3+(aq) + 3OH-(aq)
C. Cd(OH)2(s) <---> Cd +2(aq)+2OH-(aq)
D. Cd2+(aq) + 2OH-(aq) <---> Cd(OH)2(s)
E. Cd+(aq) + OH-(aq) <---> CdOH(s)

1 Answer

C:

#"Cd"("OH")_2(s) rightleftharpoons "Cd"^(2+)(aq) + 2"OH"^(-)(aq)#

Explanation:

For a given solubility equation:

#wAB(s) -> xA^(z+)(aq)+ yB^(z-)(aq)#

#K_(sp)=[A^(z+)]^x[B^(z-)]^y#

Same as every other equilibrium expression, solids and liquids are included as #1#, and the ratio must represent products/reactants . Also the coefficients of the stoichiometric equation must be represented as exponents in the K expression

The reason why D is incorrect is because the ratio of products over reactants for #K_(sp)# would be:

#K_(sp)=1/([Cd^(2+)][OH^-]^2)#