Topic-7

Predicting Whether Precipitate Will Form Or Not

 Key Concepts

1. Q = the product of the ion concentrations which actually exist in solution = “what we have”

 2. Ksp = the product of ion concentrations required to establish a solubility equilibrium = “what we need to form a saturated solution”

 3. Q < Ksp

 In this case “what we have” is less than “what we need to form a saturated solution” so that there are not enough ions in solution to form a precipitate.

 conclusion: A precipitate cannot form if Q < Ksp

 4. Q = Ksp

 In this case “what we have” is just equal to “what we need to form a saturated solution”. The minimum possible amount of precipitate forms at this point.

 Conclusion: A barely saturated solution is formed if Q = Ksp

 5. Q > Ksp

In this case “what we have” is greater than “what we need to form a saturated solution” and there is an excess of ions, over and above the amount needed to form a precipitate. Therefore, a precipitate must form and will continue to form until the excess ions have been removed from solution and the value of Q has been reduced down to the value of Ksp.

 Conclusion: A precipitate will form if Q > Ksp.


Activity-1

Watch Tutorial video


Activity-2 (optional)

You should do following worksheet to check your understanding of this topic. Self Assessment

Activity -3

Complete the following assignment and submit online.

Ktrial Assignment

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