2.6 Reversible reactions, industrial processes and important chemicals Flashcards
What is the Haber Process?
the production of ammonia
What are the 5 stages in the Haber Process (industrial)?
- Nitrogen and Hydrogen enter the chamber in a 1:3 ratio
- Gases are compressed
- Converter containing Fe catalyst causes hydrogen and nitrogen to react forming gaseous ammonia
- Cooling tank condenses ammonia into a liquid
- Unreacted gases are recycled.
What is the optimum temperature of this process?
450*C
What is the optimum pressure of this process?
200atm
What is the catalyst in this process?
Fe/Iron
Where does the nitrogen come from? The hydrogen?
Nitrogen- the air
Hydrogen- natural gases
What type of reaction is used in making ammonia?
reversible
What is the word equation in the Haber process?
Nitrogen + Hydrogen ⇌ Ammonia
What is the symbol equation in the Haber process?
N(2) + 3H(2) ⇌ 2NH(3)
What is meant by a closed system?
nothing can enter nor leave the system, eventually a dynamic equilibrium will be established
Is nitrogen + hydrogen ⇌ ammonia exothermic or endo?
Exothermic
is ammonia ⇌ nitrogen + hydrogen exo or endo?
Endothermic
At low temperature is the yield high? Is the rate high?
High yield but slow rate of reaction
At high temperature is the yield high? Is the rate high?
Low yield but fast rate of reactions
When does pressure only affect reactions?
Both reactants and products are gases
What side does an increase in pressure favour?
increase in pressure favours side of fewer moles
What does high pressure do to ammonia’s yield?
The higher the pressure, the higher the yield
Why is high pressure so expensive?
all the machinery and power needed for the reaction
Does the direction go forward or backwards when : The pressure is increased?
Forward, the reaction makes more ammonia
Does the direction go forward or backwards when : The ammonia is removed?
Forward, the reactions makes more ammonia
Does the direction go forward or backwards when : The temperature is increased?
Backwards, the reaction is endothermic
Does the direction go forward or backwards when : There are more molecules on the left?
Forward, removes extra molecules
Does the direction go forward or backwards when : The reaction is cooled?
Forward, reaction makes more ammonia/exothermic
Does the direction go forward or backwards when : The pressure is reduced?
Backwards, the pressure is higher on the left side
Does the direction go forward or backwards when : The number of molecules on the left decreases?
Backwards, reaction favours less molecules/replaces molecules
Why aren’t low temperatures used in the Haber process?
rate is too slow
Why aren’t high temperatures used in the Haber process?
yield is too low
Why isn’t low pressure used in the Haber process?
lower yield of ammonia
Why isn’t high pressure used in the Haber process?
More pressure on ammonia so no balance/expensive
What is the Contact process?
The production of sulphuric acid
What are the raw materials used in the Contact process?
sulphur, air and water
What happens in the first stage of the Contact process? What is the symbol equation for this?
Sulphur burned to make sulphur dioxide, (can be extracted from impurities in crude oil or natural gases)
S + O2 -> SO2
What happens in the second stage? What is the symbol equations for this?
Sulphur dioxide turned in sulphur trioxide, catalyst vanadium oxide is used
2SO2 + O2 ⇌ 2SO3
What happens in the third stage? What is the symbol equation for this?
Sulphur trioxide reacts with water to form sulphuric acid
SO3 + H2O -> H2SO4
Why can’t sulphur trioxide be added directly to water?
It’s highly dangerous and clouds of sulphuric acid occur.
What is sulphur trioxide added to instead and what is made?
Added to concentrated sulphuric acid called oleum
SO3 + H2SO4 → H2S2O7
What is oleum then added to?
water to make sulphuric acid again
H2S2O7 + H2O → 2H2SO4
Why can’t the temperature be low?
It’s an exothermic reaction so low temp is better but low rate
What is the optimum temp in the contact process? pressure?
450*C
2atm
Why is the pressure so low?
To reduce expense and explosion risks
What are the uses of sulphuric acid?
detergents
paints
dyes
plastics
artificial fibres
dehydrating agent
fertilisers
What happens to sugar and concentrated sulphuric acid?
Steam released, black liquid produced that turns into black solid
What colour did the sugar go from?
white - orange - black
Why has the sugar turned black?
Hydrogen and oxygen removed so only carbon remains
What happens to hydrated copper sulphate and concentrated sulphuric acid? What’s all that remains?
copper sulphate goes from blue to white
only copper sulphate remains
What is the reaction for making fertilisers?
NH3 + 2O2 -> HNO3 + H2O
Apart from eutrophication, what other risks are there with nitrate fertilisers?
Nitrate fertiliser gets into our drinking water and causes possible health risks such as stomach cancer and ‘blue baby disease’.
