Lawn Fertiliser Titration.. Source of Errors. (1 Viewer)

[darntartmui]

does anyone know of some source of errors for this experiment and how to improve them?

 

[Dreamerish*~]

Problems

• Some sulphate may have not have been dissolved.
• When the insoluble material was filtered off, it would have been wet, taking a small amount of dissolved sulphate with it.
• Chemicals may have been lost during the process.
• The reaction of Ba²⁺ and SO₄^2- is reversible - hence it does not occur to completion.

Solutions

• Stir well, and for a good length of time to ensure that the maximum amount of sulphate have been dissolved.
• Restore the water from the filtered material back into solution. (not too sure about this one)
• Take care when handling chemicals to ensure that they are completely transferred from one container to another.
• Add excess barium chloride (or barium nitrate) to force reaction to completion.

Okay, that was the best I can do. I hope it helped to some extent.

 

[xiao1985]

Ba 2+ also forms ppt with PO4 3-... hence adaquate amount of acid is added to diminish the PO4 3- present

 

[darntartmui]

hey, cool.. those helped. but i think that really applies more to precipritation reactions right?? hm.. im doing titration and using the indicator Alizarin Red S

..??

 

[Dreamerish*~]

hey, cool.. those helped. but i think that really applies more to precipritation reactions right?? hm.. im doing titration and using the indicator Alizarin Red S

..??

Oops.

I'm going to lose a crapload of marks because I don't read questions properly.

Hmm... titration aye? *strokes beard* Well, I never learned to do the lawn fertiliser thing by titration, but just to point out some main sources of error in titration in general:

PROBLEMS

• Not washing burette properly, resulting in a higher titre.
• Not washing pipette properly, resulting in a lower titre.
• Not washing the conical flask properly.
• The volumes may have been slightly inaccurate.

SOLUTIONS

• Rise burette well, twice with distilled water, and then with the substance which it will hold. Rinsing it with water before filling it will dilute the solution.
• Rise pipette twice with distilled water, and then with the substance which it will hold. Rinsing it with water before filling it will dilute the solution.
• Rinse the conical flask with distilled water, not[/I] with the solution it will hold. Rinsing it with the solution will increase the number of moles in the flask, making calculations inaccurate.
  [*]Make sure that when measuring volumes, the measurement taken is on the bottom of the meniscus. Also remember to take out the filtering funnel immediately after filling the burette - it could drip solution into the burette, increasing the volume.
  

 

[darntartmui]

hey thanks~~ wish me luck with my presentation due tomo~