Equilibrium Constants

Question 1

What is an equilibrium constant

Answer 1

A reaction has a fixed equilibrium constant which describes the extent to which the reaction proceeds

Question 2

How is the equilibrium constant calculated in the equation aA + bB -> cC + dD

Answer 2

K = ([C]^c x [D]^d) / ([A]^a x [B]^b)

Question 3

What do you need before you can calculate the equilibrium constant

Answer 3

The system must be at a balanced equilibrium

Question 4

Br2(g) <=> 2Br(g)

1 mole of Br2 is in a 1 litre flask, 1% dissociation occurs.

What is k

Answer 4

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

Question 5

2NOCl_(g) <=> 2NO_(g) + Cl_2(g)

2 moles of NOCl in a 1 moldm^-3 flask. 0.66 moles of NO are produced.

What is k

Answer 5

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