I had read about Solubility, and I found that Solubility is not Molarity (because previously I believe that both are same thing). But, they have a big difference (source : https://en.wikipedia.org/wiki/Solubility ). Thus, now I'm in confusion that if solubility and Molarity is different terms, then the Solubility Product and Equilibrium Constant will also be different, for the same reaction, because while writing the Equilibrium constant we use Molarity (source: https://www.calstatela.edu/sites/default/files/dept/chem/11winter/201/jan20.pdf ) So, now I had tried to find out the relation between two of them. But, I am unable to find any such relations. So, anyone can help me to find out the relation between the Solubility product and Equilibrium Constant for a reaction.

New Question @Poutnik sir, please see this question (pasted below) enter image description here

So, in this question they had asked about the mass of Silver Iodate (AgIO3) in 100 mL saturated solution. But, when I saw the answer of this question (pasted below), then they are defining Solubility as the Moles of Salt present in 1000 mL of solution. But, you had defined solubility as the maximum mass of substance in 100 mL solvent.
Solution of the question.

Solution of the question.
So, I'm confused in the definition of Solubility, and which I can use always to get correct answers. Please help.


1 Answer 1


Solubility product is an equilibrium constant in a specific form for precipitation reaction of respective ions. Both can be expressed in terms of molarity, but more exactly in unitless activities.

Solubility is maximum mass of substance able to be dissolved in the given volume off solvent, usually 100mL.

Molarity is molar concentration as (molar) amount of substance in 1 L of the solution.

  • $\begingroup$ Sir, please check my question, I had added some new data that will help you to understand my query more clearly now. $\endgroup$ Commented Mar 17, 2022 at 20:39
  • $\begingroup$ @UJJWALMISHRA The analytical composition of a saturated solution, expressed in terms of the proportion of a designated solute in a designated solvent, is the solubility of that solute. The solubility may be expressed as a concentration, molality, mole fraction, mole ratio, etc. goldbook.iupac.org/terms/view/S05740 $\endgroup$
    – Poutnik
    Commented Mar 17, 2022 at 21:02
  • $\begingroup$ See also en.wikipedia.org/wiki/Solubility_table // There is multiple equivalent ways how to express solubility. The way of g/100 mL of solvent is one of the most common. $\endgroup$
    – Poutnik
    Commented Mar 17, 2022 at 21:07
  • $\begingroup$ Solubility is a constant at given temperature. Molarity can be any numerical value between zero and the solubility. $\endgroup$
    – Maurice
    Commented Mar 17, 2022 at 21:08

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