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Solubility Ksp Calculations

How do you complete a solubility Ksp problem?

What is the solubility of aluminum hydroxide in water at 25 degrees Celsius if the Ksp is 3 x 10^-34? What is the concentration of Hydroxide at equilibrium?

What is the concentration of a sulfide ion in a 1L solution of cuprous sulfide to which .03mol of cuprous nitrate has been added? The Ksp of cuprous sulfide is 8 x 10^-37

Please post all steps. Thanks!

Solution Preview

The solution is attached.

Thanks for the good questions.

First you need to write and balance the precipitate dissociation reaction.

Aluminum Hydroxide - my first question is, what is the compound formula?
If I do not know there are a number of routes to the answer. One is an internet search and the formula is Al(OH)3

So we have Al(OH)3-----------> Al(III) + 3OH(-)

Ksp = [Al(III)][OH]^3 where the brackets signify concentration

Now the Ksp on order of 10^(-34) means this barely dissociates in water at 25C.

If we start with 1 mole of aluminum hydroxide in 1 Liter water or 1M, we see ...

Solution Summary

This solution is provided in 480 words in an attached .doc file. It uses the balancing of the precipitate dissociation reaction as a step to solving the problem.