Agata Łuszczyńska 8.12.2007

Batory High School I ib 2 h

Determining the cations from

1^st group of Fresenius

	DCP	CE
Asp1
Asp2
Asp3

In this experiment we were determining which cations of 1^st Fresenius group we had in a given test-tube.

Data collection and processing:

Solution

1. ↓ + HCl

white precipitate

↓+ hot water

I decantate the solution

white precipitate solution

2. ↓+ NH_{3 (aq)} 2. ↓ + KI

solution yellow ppt→ PbI₂↓

ppt dissolved

3. ↓+ HCl

white ppt → AgCl↓

Reactions:

1. Pb²⁺ + 2Cl ^- → PbCl₂↓

Ag⁺ + Cl ^- → AgCl↓

2. PbCl₂ + 2I ^- → PbI₂↓ + 2Cl ^-

AgCl + 2NH₃ → [Ag(NH₃)₂]Cl↓

3. [Ag(NH₃)₂]Cl + 2H⁺ → AgCl↓ + 2NH₄

Conclusion and evaluation:

The final procuts were AgCl↓ and PbI₂↓. That means, that in the beggining in the test-tube I had cations of Ag⁺ and cations of Pb²⁺ mixed together.

To improve the experiment I would use bigger amounts of each reagent. Also it would be wise to split the solution into two test-tubes and repeat the experiment twice, to be sure of the outcome.

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