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Question I received from an SDN student
So Ca(OH)2, Sr(OH)2, and Ba(OH)2 are strong bases. Strong bases completely dissociate to release OH ions. Yet, these compounds are only "slightly" soluble and form precipitates. I guess I am struggling to understand how they can be labeled strong bases that completely dissociate and yet not be completely soluble in water?
Answer:
Your question is an excellent one. Common strong bases include all Group 1 hydroxides. LiOH, NaOH, KOH, CsOH, and RbOH.....as well as some Group 2 hydroxides.... Ca (OH)2, Ba(OH)2, and Sr(OH)2. Who says a strong base must dissolve 100% in water ? A base is said to be strong however , it does not mean the compound completely dissolves in water! For example, some species are only slightly soluble in water, yet are strong electrolytes. This means that not very much dissolves, but all that does dissolve breaks into ions !!!! Most hydroxides are horrible in water,,,,,and do not dissolve much at all. The above bases dissolve fairly well.
I hope this helps.
Dr. Romano
So Ca(OH)2, Sr(OH)2, and Ba(OH)2 are strong bases. Strong bases completely dissociate to release OH ions. Yet, these compounds are only "slightly" soluble and form precipitates. I guess I am struggling to understand how they can be labeled strong bases that completely dissociate and yet not be completely soluble in water?
Answer:
Your question is an excellent one. Common strong bases include all Group 1 hydroxides. LiOH, NaOH, KOH, CsOH, and RbOH.....as well as some Group 2 hydroxides.... Ca (OH)2, Ba(OH)2, and Sr(OH)2. Who says a strong base must dissolve 100% in water ? A base is said to be strong however , it does not mean the compound completely dissolves in water! For example, some species are only slightly soluble in water, yet are strong electrolytes. This means that not very much dissolves, but all that does dissolve breaks into ions !!!! Most hydroxides are horrible in water,,,,,and do not dissolve much at all. The above bases dissolve fairly well.
I hope this helps.
Dr. Romano
