🎯 Objective
Study the equilibrium shift in cobalt chloride system by changing temperature and chloride ion concentration.
Theory
[Co(H₂O)₆]²⁺
+ 4Cl⁻ ⇌
[CoCl₄]²⁻
+ 6H₂O
ΔH = +ve (Endothermic)
[Co(H₂O)₆]²⁺
Pink/Rose colored
[CoCl₄]²⁻
Blue colored
⚠️ Safety
- Cobalt(II) salts are toxic and a suspected carcinogen — avoid skin contact, never taste, wash hands after use.
- Concentrated HCl is corrosive and gives off irritating fumes; add it in a fume cupboard and wear goggles.
- Heat the tube gently in a water bath, not a naked flame; point the mouth away from yourself and others.
- Hot glassware looks the same as cold — handle with care.
- Cobalt solutions are heavy-metal waste — collect in the labelled container, do not pour down the sink.
Le Chatelier's Principle
A stress (change in temperature or concentration) shifts the position of
equilibrium in the direction that partially opposes that change.
Use it to predict the shift yourself before you act.
🔮 Predict before you experiment
The forward reaction [Co(H₂O)₆]²⁺ + 4Cl⁻ ⇌ [CoCl₄]²⁻ + 6H₂O is endothermic. Apply Le Chatelier's principle, then lock your prediction to unlock the controls.
Temperature
25°C
Cold
Hot
[Co(H₂O)₆]²⁺
→
←
[CoCl₄]²⁻
🔥
❄️
Pink Solution
[Co(H₂O)₆]²⁺ dominant
Add Chloride Ions (Cl⁻)
📊 Current State
Temperature:
25°C
[Cl⁻] Level:
Normal
Dominant Species:
[Co(H₂O)₆]²⁺
Color:
Pink
Lab Notebook
Observations will appear here...