Solubility Product

1. As you learned earlier this year some substances dissolve and others don't - at least they don't seem to. In fact, everything dissolves at least a little bit. Those substances which appear to not dissolve just dissolve too little for us to observe with our eyes.
2. One way of quantifying how well substances dissolve is to calculate the equilibrium constant for the chemical equation which describes their dissolving.
3. Let's use Silver Chloride for example: AgCl_(s) Ag⁺¹_(aq) + Cl^-1_(aq)
   1. The K value for describing the dissolving process is given a special name: Ksp.
   2. The Ksp for the above reaction is: Ksp = [Ag⁺¹][Cl^-1].
   3. If the Ksp for a substance is large then it is quite soluble. If it is very small then we would call the substance insoluble. The Ksp for AgCl is 1.6 x 10^-10 at 25°C, a very insoluble compound.
4. Sample calculations:
   1. Calculate the concentration of silver ion at room temperature (25°C) in a saturated solution of silver chloride. Click here for answer.
   2. Calculate the concentration of fluoride ion for BaF₂ if its Ksp is 2.4 x 10^-5 at 25°C. Click here for answer.