Agata Łuszczyńska 8.12.2007

Batory High School I ib 2 h

Determining the cations from

1^st group of Fresenius

from different test-tubes

	DCP	CE
Asp1
Asp2
Asp3

In this experiment we had to determine which cations of 1^st Fresenius group we had in given test-tubes.

Data collection and processing:

1.

Test-tube number	+ HCl	+ NH3 (aq)	Identified cation
1	No ppt	none	→ H2O
2	White ppt	Dissolved	→ Ag^+
3	White ppt	dissolved	→ Ag^+
4	White ppt	Black ppt	→ Hg^+
5	White ppt	Black ppt	→ Hg^+

2.

Test-tube number	+ KI (I^-)	Identified cation
1	none	→ H2O
2	Light yellow	→ Ag^+
3	Light yellow	→ Ag^+
4	Dark yellow	→ Hg^+
5	Dark yellow	→ Hg^+

Reactions:

test-tubes 2 and 3

1. Ag⁺ + Cl ^- → AgCl↓

AgCl↓ + 2NH_{3 (aq)} → [Ag(NH₃)₂]

2. Ag⁺ + I ^- → AgI↓

test-tubes 4 and 5

1. Hg₂²⁺ + 2Cl ^- → Hg₂Cl₂↓

Hg₂Cl₂↓ + NH_{3 (aq)} → black ppt

2. Hg₂²⁺ + 2I ^- → Hg₂I₂

Conclusion and evaluation:

From the experiment we determined that in the 1^st test-tube was water, in the 2^nd and 3^rd silver cations annd in the 4^th and 5^th mercury cations.

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

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