Topic 4 - Gases, Reversible, Reactions And Ammonia Flashcards
What is a reversible reaction?
The products of the reaction can themselves react to produce the original reactants
What is the formula for moles (gases)
Volume (in dm-3) = Moles of gas x 24
What is a dynamic equilibrium
if reversible reaction takes place in a close system (none of the reactants/products can escape) then a sate of equilibrium will always be reached.
This is when the amounts of reactants and products will reach a balance and stay there.
A dynamic equilibrium is when products are still taking place in both directions but the overall effect is nil because both reactions cancel each other out, they are taking place at the same rate
What does raising the temperature in a reversable reaction do?
the endothermic reaction will be favoured to use up the extra heat
What does raising the pressure in a reversible reaction do
it will favour the reaction which produces less volume
Why are catalysts used in reversible reactions
high temp and pressure wanted to increase rate of reaction but they can change the position of the equilibrium which can reseult in less product.
Catalysts speed up both forward and backward reactions by the same amount so equilibrium is reached quicker but still make the same amount of product
What is the Haber process
process that uses nitrogen and hydrogen to make ammonia
What is the equation of the haber process
N2(g) + 3H2(g) <=> 2NH3 (g) (and heat)
What are the condition used for the Haber process
pressure 200 atm
temp: 450*C
Catalyst: Iron
High pressure favours the forward reaction so pressure is as high as possible to give the best %yeild without making the plant too expensive.
Forward reacition exothermic so raising temp will move equilibrium wrong way but low temp means slow rate of reaction so comprimise has to be made to get acceptable % yeild in an acceptable time
In what state is ammonia produced in?
gas but cools in condenser, is liquified and removed.
What is ammonia used for?
Nitrogenous fertilisers
What are the problems with nitrogenous fertilisers
causes eutrophication
Causes excessive growth of algae which blocks sunlight so plants below surface die (stop photosythesising). More decating matter = more bacteria which use up oxygen so aquatic animals die
