Le Chatelier's Principle

Lab Brief #3

🎯 Your mission

Run the experiment. Find out what really happens.

⚡ The twist

Nature loves to surprise the careful watcher.

What you'll learn

If a system at equilibrium is disturbed, it shifts to oppose the change. Raise the concentration of a reactant and the forward reaction is favoured; raise the temperature and the endothermic direction is favoured; raise the pressure and the side with fewer gas molecules wins.

Key words

Le Chatelier's principle
A system at equilibrium shifts to oppose any change imposed on it.
position of equilibrium
The relative amounts of reactants and products present at equilibrium.

Make a hypothesis first

Before you start: write down what you think will happen, and why.

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

cobalt chloride solution
concentrated hydrochloric acid
water
test tubes
water bath
ice bath

Get ready

⚠️ Safety first

Cobalt compounds are toxic and possibly carcinogenic, and concentrated acid is corrosive — teacher demonstration in a fume cupboard only.
Observers must wear goggles and stand back.

Step 1 of 4 · Read

Think about what you just learned: say what "Le Chatelier's principle" and "position of equilibrium" mean in your own words before you start.

Step 2 of 4 · Do

Add acid and then alkali to a cobalt chloride equilibrium, and warm and cool it, recording the colour after each change. Predict each shift with Le Chatelier's principle before you observe it.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 2

Increasing the pressure on a gaseous equilibrium shifts it towards the side with:

How sure are you?😐 maybe

Question 2 of 2

Raising the temperature favours the direction that is:

How sure are you?😐 maybe

Mind = blown

🔬 The more you look, the more nature shows you.

Nice work!

You got 0 of 2 right.

Next: The Haber Process All lessons

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✨ More to explore

🌍 Where you see this in real life: This shows up in your everyday life more than you'd think.

🏆 Stretch challenge (try it this week): Try one experiment in real life this week — even a tiny one.

👨‍👩‍👧 For the dinner table: “What's the most surprising thing you learned today?”

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