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I/GCSE Chemistry Chapter Analysis - Chapter 2: Inorganic Chemistry - Chemical Tests (Part 2)
For I/GCSE Chemistry, you should know:
Now, let's move onto the second part of the sub-topic of chemical tests.
Chemical Tests for Ions
In addition to the tests for gases we discussed previously, there are also various chemical tests used to identify the presence of specific ions in a solution. Let's go through these tests:
- Ammonium (NH4+) ion:
- Test: Add a few drops of sodium hydroxide (NaOH) solution to the solution containing the ammonium ion.
- Observation: The solution will release ammonia gas (NH3), which can be detected by the pungent odor or by the whitening of a damp red litmus paper.
- Explanation: The sodium hydroxide reacts with the ammonium ion, producing ammonia gas:
NH4+ + OH- → NH3 + H2O
2. Copper (Cu2+), Iron(II) (Fe2+), and Iron(III) (Fe3+) ions: - Test: Add a few drops of sodium hydroxide (NaOH) solution to the solution containing the metal ion.
- Observation:
- Cu2+: A blue-green precipitate of copper(II) hydroxide (Cu(OH)2) will form.
- Fe2+: A pale green precipitate of iron(II) hydroxide (Fe(OH)2) will form.
- Fe3+: A reddish-brown precipitate of iron(III) hydroxide (Fe(OH)3) will form.
- Explanation: The sodium hydroxide reacts with the metal ions, forming the respective metal hydroxides:
Cu2+ + 2OH- → Cu(OH)2
Fe2+ + 2OH- → Fe(OH)2
Fe3+ + 3OH- → Fe(OH)3
3. Chloride (Cl-), Bromide (Br-), and Iodide (I-) ions: - Test: Add a few drops of acidified silver nitrate (AgNO3) solution to the solution containing the halide ion.
- Observation:
- Cl-: A white precipitate of silver chloride (AgCl) will form.
- Br-: A pale yellow precipitate of silver bromide (AgBr) will form.
- I-: A yellow precipitate of silver iodide (AgI) will form.
- Explanation: The silver nitrate reacts with the halide ions, forming the respective silver halides:
Cl- + AgNO3 → AgCl + NO3-
Br- + AgNO3 → AgBr + NO3-
I- + AgNO3 → AgI + NO3-
4. Sulfate (SO42-) ion: - Test: Add a few drops of acidified barium chloride (BaCl2) solution to the solution containing the sulfate ion.
- Observation: A white precipitate of barium sulfate (BaSO4) will form.
- Explanation: The barium chloride reacts with the sulfate ion, forming the insoluble barium sulfate:
SO42- + BaCl2 → BaSO4 + 2Cl-
5. Carbonate (CO32-) ion: - Test: Add a few drops of hydrochloric acid (HCl) to the solution containing the carbonate ion.
- Observation: The solution will fizz or bubble, indicating the release of carbon dioxide (CO2) gas.
- Explanation: The hydrochloric acid reacts with the carbonate ion, producing carbon dioxide gas:
CO32- + 2HCl → CO2 + H2O + 2Cl-
By understanding and practicing these chemical tests for various ions, you can effectively identify the presence of different inorganic substances, which is crucial in the field of IGCSE Chemistry.
Work hard for your I/GCSE Chemistry examination!
End of analysis. Great!
