6.0 Equilibria Flashcards
In a chemical reaction, what does this symbol, ⇌,
show?
Reversible reaction
Define a dynamic equilibrium
A reversible reaction in a closed system where
both the forward and reverse reaction have the
same rate
The concentration of reactants and products
remains the same
What is Le Châteliers principle?
If a factor affecting the position of an equilibrium is
altered, the position of the equilibrium shifts to oppose
the effect of the change
What according to Le Châtelier’s principle will happen to a dynamic equilibrium if the concentration of one of the reactants is increased?
Le Châtelier’s principle state that the equilibrium will
move in the direction that tends to reduce the
concentration of this reactant
What according to Le Châtelier’s principle will happen to a dynamic equilibrium if the concentration of one of the reactants is decreased?
Le Châtelier’s principle state that the equilibrium will
move in the direction that tends to increase the
concentration of this reactant
What according to Le Châtelier’s principle will happen to a dynamic equilibrium if the pressure on the system is increased?
• Le Châtelier’s principle states that if the pressure
on this system increases, the position on the
equilibrium moves to decrease the pressure
• This means that it will shift in the direction with
the fewest gas molecules.
What according to Le Châtelier’s principle will happen to a dynamic equilibrium if the pressure on the system is decreased?
• Le Châtelier’s principle states that if the pressure
on this system decreases, the position on the
equilibrium moves to increase the pressure
• This means that it will shift in the direction with
the most gas molecules
What according to Le Châtelier’s principle will happen to a dynamic equilibrium if the temperature on the system is increased?
• Le Châtelier’s principle states that if the
temperature on this system increases, the
position on the equilibrium moves to decrease the
temperature
• This means that it will shift in the direction that
cools the system down i.e. the endothermic
direction
What according to Le Châtelier’s principle will happen to a dynamic equilibrium if the temperature on the system is decreased?
• Le Châtelier’s principle states that if the
temperature on this system decreases, the
position on the equilibrium moves to increase the
temperature.
• This means that it will shift in the direction that
heats the system up i.e. the exothermic direction.
What effect does a catalyst have on the position of a
dynamic equilibrium?
• No effect on equilibrium position
• Both forward and reverse reaction rates are
increased equally
Why is a compromised temperature often used for an industrial equilibrium process such as the Haber
process?
A compromised temperature is often used to produce an acceptable yield in a reasonable timeframe even if lowering the temperature slows down the rate of reaction
Why is a compromised pressure often used for an
industrial equilibrium process such as the Haber
process?
A compromised pressure is often used to produce an acceptable yield to keep costs down as raising the pressure means stronger, more expensive equipment is needed
What is Kc?
The equilibrium constant
Write an expression for Kc for the following general
reaction? aA + bB ⇌ cC+ dD
Kc = [C]c[D]d
[A]a[B]b
What do the square brackets, [], around a substance
indicate in an equilibrium expression?
Its concentration in moldm-3
What are the units for Kc for the following reaction?
A + 2B ⇌ 2C + D
No units
What are the units for Kc for the following reaction?
A + 2B ⇌ 2C
mol-1 dm³
What affect does changing the following have on the
value of Kc?
a) Temperature
b) Concentration
c) Catalyst
a) c) Kc stays the same
Kc increases or decreases depending upon
whether the reaction is exothermic or
endothermic
b) Kc stays the same
For an exothermic reaction what affect does
increasing the temperature have on Kc?
Kc decreases
For an endothermic reaction what affect does
increasing the temperature have on Kc?
Kc increases
