Reversible Reactions & Equilibria

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What is dynamic equilibrium?
If they take place within a closed container, reversible reactions will eventually reach a state of dynamic equilibrium. This is when the forwards reaction and the reverse reaction are taking place at the same rate (speed).
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What is ammonia used for?
Ammonia, NH3, is a very important chemical. It is used in the manufacture of fertilisers, explosives, dyes, medicines and a variety of other chemicals.
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Why do we need ammonia?
It has been estimated that one third of the world’s population rely on food grown using synthetic fertilisers. Without ammonia, millions of people would starve.
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How is ammonia produced?
Ammonia is produced in the Haber process by reacting hydrogen with nitrogen. This is difficult because nitrogen is such an unreactive gas. The chemical equation is: nitrogen + hydrogen (Equilibrium symbol) ammonia
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What is the haber process?
The Haber process is an artificial way of ‘fixing’ unreactive nitrogen from the air and turning it into useful chemicals that plants can absorb and use when they build protein molecules in their cells.
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What is the symbol equation for the haber process?
N2(g) + 3H2(g) (Equilibrium symbol) 2NH3(g) The reaction is reversible
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Where soes the nitrogen and hydrogen come from?
The nitrogen comes from the air. The hydrogen is produced in a reaction between methane (natural gas) and steam.
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How does pressure & temperate affect the yield of ammonia in the haber process?
When the pressure is increased, the yield increases. When the temperature is increased, the yield decreases.
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How can recylcling increase the yield of ammonia?
the yield is further increased by recycling the unreacted hydrogen and nitrogen after they have been separated from the ammonia
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What catalyst is used in the haber process?
An iron catalyst is used to increase the rate of the reaction. The catalyst does not affect the yield of ammonia.
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Why use a catalyst in the haber process?
The catalyst does not affect the yield, but it does increase the rate of the reaction. This allows a lower temperature to be used and using a lower temperature allows the yield to be maximised as well as saving money on energy costs.
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What are 'nitrogen fixing' bacteria?
So-called ‘nitrogen-fixing’ bacteria are able to ‘fix’ nitrogen from the air, at room temperature and pressure, using enzymes.
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Why is using 'nitrogen fixing' bacteria to make ammonia better?
These conditions are much cheaper than the high temperature and pressure used in the Haber process. If scientists could find a way to use these enzymes on an industrial scale, this would save a lot of energy, fossil fuels and money.
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What is an environmental impact of the haber process?
Making ammonia using the Haber process requires a lot of energy, which usually involves burning fossil fuels. This releases carbon dioxide which causes global warming. Oxides of nitrogen are also emitted during the process.
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What is a risk of using fertilisers?
The widespread use of fertilisers can cause a type of pollution called eutrophication.
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What is eutrophication?
This is when fertilisers are washed off fields and into rivers and lakes, causing algae to grow. The algae die off when they have exhausted the nutrients. The algae are then decomposed by aerobic bacteria, which use up all the oxygen - ecosystem dies
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What is ammonia used for?

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Ammonia, NH3, is a very important chemical. It is used in the manufacture of fertilisers, explosives, dyes, medicines and a variety of other chemicals.

Card 3

Front

Why do we need ammonia?

Back

Preview of the front of card 3

Card 4

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How is ammonia produced?

Back

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Card 5

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What is the haber process?

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