Virtual Post Lab Exp 9: Solubility Product and Thermodynamics

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Virtual Laboratory Handout

Experiment 9: Solubility Product Vlab Tips

Before starting this lab ask yourself the following questions. Think about what this all means, don't just look for instructions.

What is the reaction the solubility product describes?

What is the maximum amount of solute that can be dissolved?

Think of two ways can you determine if your solution is saturated.

What do we mean with the equilibrium constant describing a saturated solution?

How can you determine the formula of a salt from the charge of its ions?

How can you determine the formula of a salt from the concentration of its ions?

OK, now that you have thought about the above questions lets look into them.

A saturated solution represents the maximum amount of dissolved salt that can coexist in equilibrium with its undissolved precipitate.

In general C_mA_n(s) <==> mC⁺ⁿ(aq) + nA^-m(aq)

examples: AgCl(s) <==> Ag⁺(aq) + Cl^-(aq)

Ba(OH)₂(s) <==> Ba⁺²(aq) + 2OH^-(aq)

Al₂S₃(s) <==> 2Al⁺³(aq) + 3S^-2(aq)

There are two ways you can determine if a solution is saturated.

Look at the solid. If a solid exists, it is saturated (you can also add more of the salt, and if it adds to the solid mass (none dissolves), it is saturated.

Look at the aqueous phase. Add more salt, if the quantity dissolved does not change, it is saturated (none of the added salt dissolves)

Note, you need to right click on the flask, hit thermal properties, isolate from the surroundings and set the temperature to what you want. Otherwise the system will adjust itself to 25 deg C, and your values will change as that occurs.

There are two ways to determine the formula. The easiest is to use the charge of the cation as the number of anions and the charge of the anion as the number of cations. When you do this, you need to be sure the final formula is the lowest whole number ration of cations to anions.