Comparing results of solubility test with general rules (1 Viewer)

[Chrisssss]

I have had to watch a video on solubility tests, specifically identifying cations. This included adding NaOH to a solution possessing one particular cations; ones tested for were Cu, Al, ammonium, Ba, Ca, Fe and many more. I then had to draw a table of results and answer some Q's, one being:

"Compare your results with the general solubility rules. Account for any differences".
I think most correspond with the standard expectations, however a couple seem to show odd results. For example, to my understanding Calcium hydroxide and strontium hydroxide should be insoluble, however solutions of both did form white ppt's, neither soluble in excess NaOH.

Anyone have any ideas? I'm thinking things like room temp, though right now I'm stuck for other explanations...
Help would be appreciated.

 

[samwell]

Consider contamination of the test tube or apparatus. And also hydroxide solution like Ca(OH)2[lime water] react with CO2 to form white precipitates.i hope this kinda helps. i dont think temperature has anything to do with precipitation but can affect solubility[which is negligible].

 

[Chrisssss]

Consider contamination of the test tube or apparatus. And also hydroxide solution like Ca(OH)2[lime water] react with CO2 to form white precipitates.i hope this kinda helps. i dont think temperature has anything to do with precipitation but can affect solubility[which is negligible].

Damn, I should've had that in my response, I wasn't aware of that. Thanks anyway though, I ended up being able to write something for each of odd results.