sulfate content in fertiliser experiment (1 Viewer)

[lastchance]

I've got the outline of the experiment. These are only the first few steps, but can anyone tell me when you start heating the solution and when you have to stir?

1. Weigh 0.5g of ammonium sulfate
2. Add 10ml of water and dissolve
3. Add 2ml of 1M HCl and 100ml distilled water
4. Add 25ml of 0.2M BaCl2 solution

I also need help on the reason why you need to stir the solution. Does it help increase accuracy of the experiment in any way?

 

[danz90]

I've got the outline of the experiment. These are only the first few steps, but can anyone tell me when you start heating the solution and when you have to stir?

1. Weigh 0.5g of ammonium sulfate
2. Add 10ml of water and dissolve
3. Add 2ml of 1M HCl and 100ml distilled water
4. Add 25ml of 0.2M BaCl2 solution

I also need help on the reason why you need to stir the solution. Does it help increase accuracy of the experiment in any way?

Instead of adding exactly 25mL of BaCl₂ solution, add EXCESS BaCl₂(aq) until no more precipitate is formed.

You need to stir the solution well to ensure thorough mixing, and solvation of the (NH₄)₂SO₄.
Although, more importantly, you should mix the fertiliser mixture, to ensure that a sample that is more accurate and indicative of the [SO₄^2-] of the entire fertiliser, is obtained.

Edit: Remember, you are not actually weighing Ammonium Sulfate, but rather a fertiliser sample. You add the HCl (or HNO₃) in order to remove any impurities that may cause inaccuracies. eg. Any CO_32- present will be neutralised by the acid. Otherwise, BaCO₃ would form as a precipitate, hence causing an inaccuracy.

 

[SkimDawg]

2. Add 10ml of water and dissolve

This is when you start stirring. My prac for this failed, as the teacher gave us 6M! of HCl, hence the spatula started dissolving in the solution. Stirring it helps dissolve the solid slightly.
edit: yeah danz pretty much nailed it

 

[lastchance]

Thanks to both of you =)
Good luck with the test.

This is when you start stirring. My prac for this failed, as the teacher gave us 6M! of HCl, hence the spatula started dissolving in the solution. Stirring it helps dissolve the solid slightly.
edit: yeah danz pretty much nailed it

Well at least your experiment was fun!