identifying ions (1 Viewer)

[jkwii]

got a Q from the CCHSC booklet

A solution was thought to contain either lead nitrate or calcium nitrate. Samples of the solution gave white precipitates with dilute HCl, H2SO4 and NaOH. Which of these ions is present? Explain.

 

[xiao1985]

Lead nitrate. Calcium Chloride (I believe) is soluable in water, and should not give a white ppt.

 

[Undermyskin]

Correct.

Ca(OH)2 is used to make up limewater that means it's soluble. However, according to the 'rule', it's insoluble. Conquering chem says if its solubility is assured with the [] less than 0.005M. I don't quite believe limewater has the concentration of Ca(OH)2 that low. Can anyone confirm?

 

[xiao1985]

Ca(OH)2 appears to be slightly soluable according to the sources I have. So it will be soluable in the conc of <0.1M, (heated if necessary)

 

[Undermyskin]

Thanks.

 

[brenton1987]

Calcium Chloride (I believe) is soluable in water, and should not give a white ppt.

Solid CaCl will absorb water and eventually dissolve in it, which makes it extremely soluble.

 

[Undermyskin]

It's CaCl2, mind you. I think its role in some context is akin to that of Silica with Cobalt paper or H2SO4 (conc.) to dry out ethanol.