Question #2e817

2 Answers
Apr 1, 2015

Dissolution value is the molar solubility of the substance which is the molar concentration of a saturated solution. This is calculated from the #K_(sp)# value.

Let's say you have a solid that is dissolving

#A_xB_y(s)rarr x A(aq)+ yB(aq)#

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

So in your example

#Ag_2CrO_4(s) rarr2Ag^+(aq)+CrO_4^(-) (aq)# and

#K_(sp)=[Ag^+]^2[CrO_4^(-)] #

The dissolution value will be the concentration of the chromate ion (this will also be the concentration of the solution). Each formula unit of the compound dissociates into 2 silver ions and 1 chromate ion so the concentration of silver ions will be double that.

Mathematically, the #K_(sp)# value

#K_(sp)=[Ag^+]^2[CrO_4^(-)] #

#K_(sp)=[2(3.2*10^(-5))]^2[3.2*10^(-5)] = 1.3*10^(-13) #

#K_"sp" = 1.31 ×10^(-13)#

Explanation:

#K_"sp" = 1.31 ×10^(-13)#

Every mole of Ag₂CrO₄ that dissolves forms 2 mol of Ag⁺ and 1 mol of CrO₄²⁻.

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#K_"sp" = ["Ag"^+]^2["CrO"_4^(2-)] = (6.4 × 10^(-5))^2(3.2 × 10^-5) = 1.31 ×10^(-13)#