2.2 Equilibrium and Yield

Question 1

ICE - Equilibrium Calculations

Answer 1

1. initial concentration or amount of each substance
2. x (-ve if a reactant or +ve if product)
3. coefficient of x is mole ratio
4. write any final value known at bottom
5. calculate x
6. substitute x value found

Question 2

Le Chatelier’s Principle

Answer 2

LCP predicts that closed system at equilibrium will counteract any changes made to the system and shift to a new equilibrium position

Question 3

Requirements for a system to reach eqm

Answer 3

1. closed system

2. dynamic

Question 4

What is a closed system?

Answer 4

A closed system does not allow any products or reactants to escape.
The particles are all kept in position to react

Question 5

What is equilibrium?

Answer 5

The point at which the rate of the forward reaction is equal to that of the backward reaction.
Thus the [ ] of reactants and products remains the same

Question 6

What side is favoured if:

[reactants] > [products]

Answer 6

The eqM position favours the reactants (the left)

Kc < 1

Question 7

What side is favoured if:

[reactants] < [products]

Answer 7

The eqM position favours the products (the right)

Kc > 1

Question 8

What side is favoured if:

[reactants] = [products]

Answer 8

Neither is favoured

Kc = 1

Question 9

What is the equation for the eqM constant?

Answer 9

Kc = [products]^ mole ratio / [reactants]^mole ratio

AT specific temperature

Question 10

What substances are omitted from Kc calculation?

Answer 10

Any solids in reactants or products

Question 11

What is the Kc value?

Answer 11

Ratio of products to reactants
It is a measure of yield
It shows how far right the reaction will go but gives no time indication

Question 12

Why is eqM reached?

Answer 12

As the [ ] of reactants decreases the rate of the forward reaction decreases
As more product is formed from the forward reaction the [ ] of products increases. Thus the rate of the back reaction increases.

There will be a point where the rate of f is the same as b

Question 13

Change to system if:

increase in pressure

Answer 13

Favours side will less moles

Expensive and dangerous to inc pressure

Question 14

Change to system if:

inc in temp

Answer 14

Favour endothermic side

Expensive with energy and decreases rate

Question 15

Change to system if:

inc in temp

Answer 15

Favour endothermic side

Expensive with energy and decreases rate