Reaction rates · Grade 11
Equilibrium: pink and blue cobalt
ChemAI · Worksheet
NameClassDate
Aim
Shift an equilibrium with concentration and temperature (Le Chatelier).
⚠ Cobalt chloride is toxic and concentrated HCl is corrosive: gloves and goggles.
Before you start: what do you predict will happen? Why?
What you do
| Step | What I observed | |
|---|---|---|
| 1 | Add concentrated hydrochloric acid to tube 1, one press at a time, until it turns blue. | |
| 2 | Now add water to tube 1 (5 mL at a time): the colour goes back to pink. | |
| 3 | Tube 2: add two presses of the acid (violet), then warm it in the water bath: it turns blue. | |
| 4 | Move tube 2 to the ice bath (Apparatus → Ice bath): pink again. Which direction is endothermic? |
Questions
- Write a word or symbol equation for one reaction you observed.
- Explain your most important observation using particles, ions or energy.
- Was your prediction right? What would you change to get a more reliable result?