Why do barium and sulfate only react under acidic conditions? (2 Viewers)

[leesh95]

We did a prac in class today where we Put Barium chloride and copper sulphate solutions together and added a couple of drops of HNO3 and in another test tube put them together and added a couple of drops of NaOH.

The only one where they reacted to form Barium sulphate was the acidic one.
So why is the precipitate affected by the PH?

 

[TheOptimist]

Hope this helps (I'm not too sure as to whether this is correct)
View attachment 26902

 

[leesh95]

The link doesn't work. Could you please re-post??

 

[tarod]

The sulfate ion ppt's with quite alot of other substancesin neutral/ alkaline solution. Also, carbonates in water may react with barium to form barium carbonate, preventing the formation of baSo4. Adding an acid ill decompose the carbonate.
If you make the mixture acid, you reduce the amount of interference and ensure that only barium ions are ppting.