Answer to Question #106402 in General Chemistry for Rose

Question

Consider the following reaction:

NiCO3(s) ↔ Ni2+(aq) + CO32-(aq)

what happens to the solubility of NiCO3(s) if each the following molecules is added to the NiCO3(s) solution. Does the solubility increase, decrease or remain unchanged? Consider that any changes in ionic strength can be disregarded. NiCO3(s) is sparingly soluable in water.

a. Ni(NO3)2
b. K2CO3
c. HNO3
d. NiCO3
e. KClO4

Answer 1

$NiCO_3(s) ↔ Ni^{2+}(aq) + CO_3^{2-}(aq)$

A solid can dissociate only up to when its ionic product is less than its Solubility product$(K_{sp})$

Ionic product of $NiCO_3=[Ni^{2+}]\times [CO_3^{2-}]$

If either of the ions concentration increases in water by external means,ionic product will reach its solubility product.So,$NiCO_3$ will not dissociate more or its solubility will be decreased.

a. If $Ni(NO)_3$ is added,it will dissociate and release $Ni^{2+}$ ions,and by common ion effect,solubility of $NiCO_3$ will be decreased.

b. If $K_2CO_3$ is added,it will dissociate and release $CO_3^{2-}$ ions,and by by common ion effect,solubility of $NiCO_3$ will be decreased.

c. $HNO_3$ does not have any common ion with $Ni^{2+}$ or $CO_3^{2-}$ .It will not have any effect on solubility of Nickel Carbonate in water.

d. If $NiCO_3$ itself is added,then it will have both ions in common,so the solubility will be decreased much more.

e. $KClO_4$ does not have any common ion with $Ni^{2+}$ or $CO_3^{2-}$ ,It will not have any effect on solubility of Nickel Carbonate in water.