Equilibria

Question 1

What is Le - Chateliers principle

Answer 1

A system in equilibrium will respond to oppose any change imposed upon it

Question 2

Describe the relationship between concentration and rate in a reversible reaction at equilibrium

Answer 2

-Forward and reverse reactions proceed at equal rates
-Concentration of reactants & products remain constant

Question 3

When the equilibrium lies to the left, are there more reactants or products?

Answer 3

More reactants

Question 4

When the equilibrium lies to the right, are there more products or reactants

Answer 4

More products

Question 5

What are the 3 factors that affect equilibrium position

Answer 5

Temperature
Pressure
Concentration

Question 6

What is the equation showing equilibria and forming ethanol

Answer 6

C2H4 + H2O <–> C2H5OH

Question 7

What is the equation showing equilibria and forming methanol

Answer 7

CO + 2H2 <—> CH3OH

Question 8

What are the conditions for forming ethanol in equilibria

Answer 8

T - 300 C
P - 6.5MPa
Catalyst - H3PO3

Question 9

What are the conditions for forming methanol in equilibria

Answer 9

T - 400 C
P - 5.0 MPa
Catalyst - Cr2O3 + ZnO

Question 10

What is the equation for Kc from this
aA + bB <—> cC + dD

Answer 10

[C]^c [D]^d / [A]^a [B]^b

Question 11

What is the equation for Kc

Answer 11

Concentration of products/ Concentration of reactants

Question 12

How do we calculate units of Kc

Answer 12

Each square bracket is equal to 1moldm-3, and they cancel each other out. When there are the same number of brackets on numerator and denominator, there are no units

Question 13

How does temperature affect Kc for an endothermic reaction

Answer 13

An increase in temperature increases Kc for an endothermic reaction

Question 14

Explain how temperature affects Kc for an endothermic reaction

Answer 14

-An increase in temperature for an endothermic reaction shifts the equilibrium to the right
- Meaning conc of products increase and conc of reactants decreases, therefore Kc increases

Question 15

Which side does increase temperature favour

Answer 15

Increasing temperature favours the endothermic direction

Question 16

Which side does increasing pressure favour

Answer 16

The side with fewer moles

Question 17

How does temperature affect Kc for an exothermic reaction

Answer 17

Increase in temperature means Kc decreases for an exothermic reaction

Question 18

Explain how temperature affects Kc for an exothermic reaction

Answer 18

• Increase in temperature for an exothermic reaction means equilibrium shifts to the left
• This means concentration of products decrease and concentration of reactants increases meaning a decrease in Kc value

Question 19

How does concentration affect equilibrium position

Answer 19

If concentration of reactants increases, equilibrium will shift right
If concentration of products increases, equilibrium will shift left
If concentrations of both products and reactants increase equally, no change on equilibrium position

Question 20

What are the conditions for the Haber process

Answer 20

450 C
200atm
Iron catalyst

Question 21

What is a closed system

Answer 21

Nothing can leave or enter

Question 22

What are the features of a system in a state of dynamic equilibrium

Answer 22

• Conc of reactants and products remain constant
• Forward rate = backwards rate
• Closed system