2.6 Reversible Reactions Industrial Process And Important Chemicals Flashcards
What is a reversible reaction?
The reaction that happens in both directions, the products of the reaction can react together to produce the original reactants
If the forward reaction is exothermic, what is the reverse reaction?
Endothermic
What is the Haber process
used in the industrial production of ammonia
equation for the Haber process
nitrogen + hydrogen –> ammonia
N2(g) + 3H2(g) <==> 2NH3(g)
How is ammonia collected Haber process
By cooling the reaction so the ammonia condenses into a liquid
What happens to the unreacted nitrogen and hydrogen in the Haber process
They are recycled back, so there is no waste
Conditions of the Haber process
a higher temp – 450°C - very high temp = lower yield and expensive BUT very low temp = higher yield BUT lower rate of reaction therefore 450 = compromise
a high pressure – 200 atmospheres - higher pressure = higher yield BUT higher costs & risk of explosion
an iron catalyst - used to speed up rate of reaction (compromise)
Stage one of Haber process (BBC Bitesize)
Having obtained the hydrogen and nitrogen gases (from natural gas and the air respectively), they are pumped into the compressor through pipes.
Stage 2 Haber process (BBC Bitesize)
The gases are pressurised to about 200 atmospheres of pressure inside the compressor.
Stage 3 Haber process (BBC Bitesize)
The pressurised gases are pumped into a tank containing beds of iron catalyst at about 450°C. In these conditions, some of the hydrogen and nitrogen will react to form ammonia.
Stage 4 Haber process (BBC Bitesize)
The unreacted nitrogen and hydrogen, together with the ammonia, pass into a cooling tank. The cooling tank liquefies the ammonia, which can be removed into pressurised storage vessels.
Stage 5 Haber process (BBC Bitesize)
The unreacted hydrogen and nitrogen gases are recycled by being fed back through pipes to pass through the hot iron catalyst beds again
Test for ammonia
Ammonia gas will change damp red litmus paper blue!
Test for ammonium ion
1 - add sodium hydroxide
2 - Test the gas given off
The ammonium ions convert into ammonia gas which turns the damp red litmus paper blue
4 stages of the contact process (manufacturing sulfuric acid)
- Sulfur burns in air to form sulfur dioxide gas
- Sulfur dioxide reacts with oxygen to forms sulfur trioxide gas
- Sulfur trioxide is dissolved in concentrated sulfuric acid to produce oleum
- The oleum is then diluted with water to produce sulfuric acid
Why is sulfur dioxide not directly added to water
The reaction is too violent!!
Chemical equations of the 4 stages of the contact process
- The manufacture of sulfur dioxide
Sufur + oxygen –> sulfur dioxide
S + O2 –> SO2 - The conversion of sulfur dioxide to sulfur trioxide - a reversible reaction
sulfur dioxide + oxygen <==> sulfur trioxide
SO2 + O2 <==> 2SO3 - Dissolving sulfur trioxide in concentrated sulfuric acid
Sulfuric acid + sulfur trioxide –> oleum
H2SO4 + SO3 –> 2H2S2O7 - Oleum diluted with water - to make sulfuric acid
Oleum + water –> sulfuric acid
H2S2O7 + H2O –> 2H2SO4
Conditions used at the reversible reaction of sulfur dioxide and oxygen to make sulfur trioxide
400-500 degrees C
Atmospheric pressure
Vanadium (VI) oxide catalyst
What does sulfuric acid do
Example with glucose
what type of reaction
It can be used as a dehydrating agent - removes water from a substance
Concentrated sulfuric acid takes away the elements of water leaving only carbon
C6H12O6 –> 6C(s) + H2O
water is removed as steam as reaction is exothermic
Uses of sulfuric acid
Fertilisers
Paints
Fibres
Detergents
Plastics
Dehydrating agent
What are the reaction conditions for a process a compromise between
Examples (Haber process)
Yield of production, rate of production, cost and safety
e.g. rate too slow at low temp; higher temp is a compromise between yield and rate
Higher pressures = expensive, risk of explosions - compromise between yield and cost/safety
Name of a common fertiliser and how it’s made
Ammonium sulfate - made by neutralising (add base) sulfuric acid (or other e.g. nitric - will make ammonium nitrate) with ammonia or ammonium hydroxide
With ammonia: 2NH3 + H2SO4 –> (NH4)2SO4
With ammonium hydroxide: 2NH4OH + H2SO4 —> (NH4)2SO4 + 2H2O
Advantages of fertilisers
Increases crop yield
Healthier crops
Improve soil quality
Disadvantages of fertilisers
Eutrophication
Risk of stomach cancer
Blue baby syndrome ((low oxygen levels in the blood))
