Group II Cations Analysis Simulator

Group II Cations Analysis

Precipitation of Pb²⁺, Cu²⁺, and As³⁺ using H₂S Gas in Dilute HCl.

1. Setup Experiment

Select Unknown O.S.

2. Observation

Physical State Clear Solution

Status: Standby.
Start with the Original Solution acidified with Dilute HCl. In Step 1, Hydrogen Sulfide (H₂S) gas will be passed through the solution.

3. Chemical Principles

1. Precipitation (Common Ion Effect): H₂S is passed in the presence of dil. HCl. The high H⁺ concentration suppresses H₂S ionization, yielding a very low S²⁻ concentration. This is only enough to exceed the Kₛₚ of Group II sulfides (precipitating them) while Group IV sulfides (like ZnS) remain dissolved.

M²⁺ + H₂S → MS↓ + 2H⁺

2. Group II Sub-groups: IIA (Cu, Pb) precipitates are insoluble in Yellow Ammonium Sulfide (YAS). IIB (As) precipitates dissolve in YAS.

Visual Key

Acidic Original Solution

H₂S Gas Bubbles

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