Precipitation of Al3+ and Fe3+ using NH4OH in presence of solid NH4Cl.
1. Setup Experiment
Select Unknown O.S.
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2. Observation
Physical StateClear Solution
Status: Standby.
Start with the Original Solution. In Step 1, Solid NH4Cl is added and boiled to expel gases, followed by the slow addition of excess NH4OH solution.
3. Chemical Principles
1. Precipitation (Common Ion Effect): The addition of solid NH4Cl provides a high concentration of NH4+ ions. This suppresses the ionization of the weak base NH4OH (Common Ion Effect), severely lowering the OH- concentration.
Only the highly insoluble hydroxides of Group III (Fe, Al) precipitate. Group IV/V hydroxides remain dissolved.
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