How to Use the Virtual Interface
- State Tracking: The engine tracks liquid and solid phases. Adding reagents updates the pH and visual state automatically.
- Centrifuging: If a precipitate forms, click "Centrifuge & Separate". The engine will split the solid and liquid into two new independent tabs and discard the mixed parent fraction to keep your workspace clean.
- Gas Testing: If you observe bubbles, immediately click "Test Evolved Gas" to apply chemical indicator tests (e.g., Limewater, Litmus). If you add another reagent, the gas headspace is lost.
- Heat: Toggle the Burner to simulate boiling/warming. A glowing base indicates the tube is heated. Ensure heat is ON before applying reagents that require it (e.g., NaOH for NH₄⁺).
Systematic Cation Separation
- Group I (Ag⁺, Pb²⁺, Hg₂²⁺): Ppt with dilute HCl.
- Group II (Cu²⁺, Bi³⁺, Cd²⁺, Hg²⁺, Sn²⁺, Sb³⁺): To filtrate (acidic), add H₂S. HgS is black and insoluble even in conc. HNO₃.
- Group III (Fe³⁺, Fe²⁺, Al³⁺, Cr³⁺, Ni²⁺, Co²⁺, Zn²⁺, Mn²⁺): To filtrate, add NH₃/NH₄Cl buffer, then (NH₄)₂S. Fe²⁺ gives black FeS; Fe³⁺ gives Fe₂S₃.
- Group IV (Ba²⁺, Sr²⁺, Ca²⁺): To filtrate, add (NH₄)₂CO₃.
- Group V (Mg²⁺, Na⁺, K⁺, NH₄⁺): Soluble remainder. Test specifically.
Systematic Anion Scheme
*Note: In real bench analysis, cations and anions are analyzed from separate stock portions of the original salt. While the engine allows you to mix them here for practice, be aware of complex cross-reactions.*
- Volatile Acids: Add dil HCl. CO₃²⁻ gives CO₂, SO₃²⁻ gives SO₂, NO₂⁻ gives brown NO₂, CN⁻ gives toxic HCN.
- Barium Chloride Group: BaCl₂ ppts SO₄²⁻, SO₃²⁻, PO₄³⁻, C₂O₄²⁻. Only BaSO₄ is insoluble in HCl.
- Silver Nitrate Group: AgNO₃ ppts Halides (Cl⁻ white, Br⁻ pale yellow, I⁻ yellow), also CN⁻ (white), SCN⁻ (white).
- Soluble: NO₃⁻ (Brown ring test).
Key Ion Distinctions
- Fe²⁺ vs Fe³⁺: Fe²⁺ gives green ppt with NaOH (darkens to brown in air), deep blue with K₃[Fe(CN)₆]. Fe³⁺ gives red-brown ppt, blood-red with KSCN, Prussian Blue with K₄[Fe(CN)₆].
- Al³⁺ vs Zn²⁺: Both give white ppt with NaOH, both dissolve in excess NaOH. Al³⁺ does NOT dissolve in excess NH₃; Zn²⁺ does. Aluminon gives red lake only with Al³⁺.
- Hg²⁺ vs Hg₂²⁺: Hg²⁺ gives scarlet-red ppt with KI (dissolves in excess). Hg₂²⁺ gives white calomel (Hg₂Cl₂) with HCl; turns black with NH₃.
- Co²⁺: Blue ppt with NaOH → turns pink on heating. Intense blue in amyl alcohol with KSCN. Most reliable confirmatory test.
- Gas tests: NH₃ → blue litmus; CO₂ → limewater milky; SO₂ → K₂Cr₂O₇ turns green; HCN → Prussian Blue paper; H₂S → lead acetate paper turns black.
Amphoteric Hydroxides
Al(OH)₃, Zn(OH)₂, Cr(OH)₃, and Pb(OH)₂ dissolve in both excess acid AND excess NaOH. This is a critical distinguishing property. Mg(OH)₂, Fe(OH)₂, Fe(OH)₃ do NOT dissolve in excess NaOH.