What is the difference between Qsp and Ksp?

1 Answer
Feb 25, 2017

Answer:

Well, #K_"sp"# is an actual equilibrium constant, that is experimentally measured..........

Explanation:

And #Q#, the so-called ion product, is a TRANSIENT, non-equilibrium value.

For a sparingly soluble salt, #MX_n#, certainly we can measure a constant for the equilibrium reaction for a given temperature:

#MX_n(s) rightleftharpoonsM^(n+) + nX^-#

And #K_"sp"=[M^(n+)][X^-]^n#

And likewise we so define #Q=[M^(n+)][X^-]^n#.

If #Q=K_"sp"#, then equilibrium has been reached, and no MACROSCOPIC change will occur. If #Q<K_"sp"#, then any precipitate will go up into solution. At #Q>K_"sp"#, then precipitation will occur.