2.6 - Reversible reactions, industrial processes, and important chemicals Flashcards
What is a reversible reaction?
A reaction which occurs in 2 directions
The products can react to form the original reactants
A+B ⇌ C+ D
In a reversible reaction - the amount of energy absorbed in the forward process is the same/different as the amount of energy released in the reverse process
Same
How can the direction of a reversible reaction be changed?
By changing the conditions:
Pressure
Temperature
Concentration of reactants or products
If the forward reaction is exothermic, will the backward reaction be endothermic or exothermic?
Endothermic, the same amount of energy is released
What can ammonia be used for?
To produce nitrogen-based fertilisers
How can the presence of ammonia gas be tested?
Damp red litmus paper will turn blue as ammonia is alkaline
How can the presence of ammonium ions be tested? What is the ionic equation for this?
1) Add solution containing hydroxide ions
2) Test for ammonia gas
NH4+(aq) + OH–(aq) → NH3(g) + H2O(l)
Where can nitrogen and hydrogen gas be obtained from?
Nitrogen: from air
Hydrogen gas: reacting natural gas with steam or other sources
What are the conditions required for the Haber process?
High temperature - 350°C to 450°C
a high pressure – 150 to 200 atmospheres
an iron catalyst
What happens during the Haber process?
1) Purified gases passed over iron catalyst
2) Some nitrogen and hydrogen reacts to form ammonia
3) Some ammonia breaks down into nitrogen and hydrogen (because reaction is reversible)
4) Mixture is cooled, ammonia liquefies and is removed
5) Remaining nitrogen and hydrogen recycled
What is the reaction in the Haber process?
Nitrogen + Hydrogen = Ammonia
N2 + 3H2 ⇌ 2NH3
What are the disadvantages of using a low temperature and very high pressure?
Low temp: Slower rate of reaction
High pressure: Requires high energy
What are the two things aimed to be maximized when choosing the conditions of the Haber process
Rate of reaction and yield of ammonia
Increasing the pressure of the reaction _____ (increases/ decreases) the yield of ammonia. However, if the pressure is made too high, the equipment needed to safely contain the reaction becomes very expensive.
increases
Increasing the temperature of the reaction actually ______ (increases/ decreases) the yield of ammonia in the reaction. This means that we could get a bigger yield of ammonia with a lower temperature. However, if the temperature is too low, the rate of the reaction would be so slow that it would take too long to make the ammonia.
decreases