Equilibrium Constants Flashcards
What is an equilibrium constant
A reaction has a fixed equilibrium constant which describes the extent to which the reaction proceeds
How is the equilibrium constant calculated in the equation aA + bB -> cC + dD
K = ([C]c x [D]d) / ([A]a x [B]b)
What do you need before you can calculate the equilibrium constant
The system must be at a balanced equilibrium
Br2(g) <=> 2Br(g)
1 mole of Br2 is in a 1 litre flask, 1% dissociation occurs.
What is k
k = [Br]2 / [Br2]
[initial]/moldm-3
[equilibrium]/moldm-3
Br2
1
0.99
Br
0
(0.01x2) = 0.02
There is a 1:2 ratio so you need to multiply by 2
2NOCl(g) <=> 2NO(g) + Cl2(g)
2 moles of NOCl in a 1 moldm-3 flask. 0.66 moles of NO are produced.
What is k
k = ([NO]2 x [Cl]) / [NOCl]2
[initial]/moldm-3
[equilibrium]/moldm-3
NOCl
2
(2-0.66)= 1.34
NO
0
0.66
Cl2
0
0.33
There is a 2:2 ratio of NO:NOCl so you take away the number of moles of NO produced from the number of moles of NOCl to find the number of moles of NOCl