Precipitation titrations: argentometry
Classical Quantitative Analysis · Chemistry
Study notes
In Mohr's method, why must pH be neutral (6.5–9)? Step 1: Acidic: CrO₄²⁻ → Cr₂O₇²⁻ (indicator destroyed, no red end point). Step 2: Alkaline: Ag⁺ → AgOH/Ag₂O precipitate (titrant consumed wrongly). Step 3: Neutral pH: AgCl precipitates first, then red Ag₂CrO₄ signals end. Step 4: pH window keeps both indicator and titrant honest!