Reversible reactions and equilibria Flashcards
What is a reversible reaction?
Areaction in which the products can
react to form the original reactants.
Denoted by the symbol: ⇌
How can the direction of a reversible reaction be
altered?
Changing the reaction conditions.
E.g. Temperature, pressure,
concentration.
What is meant by the term dynamic equilibrium?
Dynamic equilibrium is when the rate of the
forward reaction equals the rate of the backwards
reaction. This means the concentration of
reactants and products are constant even though
compounds are continually reacting.
What is a closed system?
A system where nothing is added or
removed. All reactants and products
remain in the reaction vessel.
Why is equilibrium only reached if the reaction takes
place in a closed system?
The closed system prevents any
reactants and products escaping so that
they are able to react continuously.
What is the Haber process?
An industrial process used to produce
ammonia (for making fertilisers).
Write the chemical equation for the reversible
reaction between nitrogen and hydrogen, forming
ammonia
N2 + 3H2 ⇌ 2NH3
Where are the sources of nitrogen and hydrogen for
the Haber process?
Nitrogen: Extracted from the air.
Hydrogen: Obtained from natural gas.
True or false? ‘The process used to form ammonia
is a reversible reaction that will never reach dynamic
equilibrium’
FALSE
The formation of ammonia is a reversible
reaction that will reach dynamic
equilibrium in a closed system.
What conditions are used for the Haber process?
- 450°C temperature
- 200 atm pressure
- Iron catalyst
Explain the effect of increasing the temperature of a
reversible reaction if the forward reaction is
endothermic
The forward reaction is endothermic so increasing the
temperature favours the forward reaction. The equilibrium
will shift towards the forward reaction and the yield of the
products will increase.
Explain the effect of increasing the pressure of a
reversible gaseous reaction
An increase in pressure will favour the reaction
that produces the least number of molecules. The
equilibrium position will shift towards the side that
produces the fewest gaseous molecules.
The equation for the Haber process is
N2 + 3H2 ⇌ 2NH3
Explain the effect of increasing the pressure on the
yield of ammonia
Increasing the pressure will shift equilibrium to
the right as there are fewer molecules of gas.
The yield of ammonia will increase.
The concentration of the reactants are increased
during a reversible reaction. What effect will this
have on the equilibrium position?
The equilibrium will shift to the right so the
product yield will increase. This will reduce
the effect of the increased concentration of
the reactants.
If there are equal gaseous molecules of the reactant
and product in a reversible reaction, what effect will
changing the pressure have on the equilibrium
position?
No effect
