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[manish.iitr]

I would like to check precipitation of CACO3 solid. The reaction at equilibrium is
CACO3(S) <--> CA++ + CO3--
Usually, to check potential for salt precipitation ionic products concentration (Qsp) is compared with solubility equilibrium constant (Ksp) value at that temperature. If Qsp > Ksp; then we can say that there is a potential for formation of salt.
I am having ambiguity about how to calculate Qsp? Is it [Ca++ ] x [CO3--] or it is square of limiting reactant concentration; for e.g. if [Ca++] = 0.5 mol/l and [CO3--] = 0.2 mol/l. Then Qsp = 0.5* 0.2 or 0.2*0.2?