Equilibrium & Industry
Reversible reactions and dynamic equilibrium, and how the Haber process makes ammonia using conditions chosen as a compromise between yield, rate and cost.
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Reactions that go both ways ⚗️
Most reactions we meet go one way: reactants turn into products and stop. But some reactions are **reversible** (shown by the ⇌ symbol): the products can react to reform the reactants. In a closed container, a reversible reaction reaches a balance called **dynamic equilibrium**. This module explores equilibrium and how it is used in industry, in the **Haber process** that makes ammonia.
The words of equilibrium 🔑
The key ideas for reversible reactions:
What is dynamic equilibrium? 🎯
What is happening at dynamic equilibrium in a closed container?
- The forward and backward reactions happen at the same rate
- Both reactions have completely stopped
- Only the forward reaction is happening
- All the reactants have been used up
Balance the Haber equation 🧱
In the Haber process, nitrogen reacts with hydrogen to make ammonia: N2 + _____ H2 ⇌ _____ NH3. The nitrogen comes from the _____ and the hydrogen from natural gas. Because the reaction is _____, not all of the gas reacts, so the unreacted gases are _____.
The Haber process 💡
The **Haber process** makes **ammonia** (NH3), which is used to make fertilisers that help feed the world. It combines **nitrogen** (from the air) with **hydrogen** (from natural gas) in a reversible reaction: **N2 + 3H2 ⇌ 2NH3** Because it is reversible, only some of the gas turns into ammonia each time, so the unreacted nitrogen and hydrogen are recycled.
The Haber conditions 🔗
- Pressure
- Temperature
- Catalyst
- Unreacted gases
- About 200 atmospheres, a high pressure
- About 450 degrees C, a moderate temperature
- An iron catalyst to speed up the reaction
- Are recycled back into the reactor
True about equilibrium? ✅
Select the TWO true statements about a reaction at dynamic equilibrium in a closed container.
- Both the forward and backward reactions are still happening
- The amounts of reactants and products stay constant
- The reaction has stopped completely
- Only products are left
A compromise: yield vs rate ⚖️
The conditions in the Haber process are chosen as a compromise between getting a good yield and a fast enough rate.
Why 450 degrees C? 📋
Why does the Haber process use a moderate temperature of about 450 degrees C, rather than a low one?
- A low temperature would make the reaction too slow
- A low temperature would give too much ammonia
- Low temperatures are more expensive to reach
- A low temperature would make it explode
Steps of the Haber process 🪜
An interactive activity.
Spot the conditions 🖍️
An interactive activity.
Set the conditions 🧭
An interactive activity.
Explain the compromise ✍️
An interactive activity.