11: Equilibrium II

Question 1

What is the equilibrium expression in terms of the partial pressure of gases in a homogenous reaction

Answer 1

Question 2

What is the Kp expression for heterogenous systems

Answer 2

Solids and liquids are ignored in Kp equations

Question 3

How can the Kp equation change

Answer 3

It only changes in the temperature of the reaction changes

Question 4

What is the equation for concentration

Answer 4

Question 5

What are the steps to calculate Kc equations

Answer 5

• Balance the equation
• Calculate the concentrations of the reactants and products at equilibrium
• Write the Kc expression
• Substitute the concentrations and stoichiometric ratio number into the equation
• Calculate and deduce the units

Question 6

How do deduce units of a Kc equation

Answer 6

Question 7

How to deduce units of Kp equations

Answer 7

Question 8

How to know if a reaction has reached equilibrium

Answer 8

• The moles of reactants and products will remain unchanged
• Concentrations of each chemical will remain unchanged
• Consequently the value of of the equilibrium constant doesn’t change

Question 9

How does a change in temperature change the Kc of an endothermic reaction

Answer 9

Question 10

How does a change in temperature change the Kc of an exothermic reaction

Answer 10

Question 11

How does change in temperature affect the equilibrium constant

Answer 11

• In exothermic reactions, increase in temperature moves the POE to the left side (reactants) increasing their concentration, which decreases the magnitude of the Kc equation, so Kc decreases
• In endothermic reactions, increase in temperature moves the POE to the right side (products) increasing their concentration, which increases the magnitude of the Kc equation, increasing Kc
• Visa Versa for decrease in temperature

Question 12

How is Kc affected if concentration changes

Answer 12

It isn’t affected as long as the other conditions stay the same (equilibrium is restored)

Question 13

How are Kc and Kp affected by changes in pressure

Answer 13

Change in pressure only affects the POE, so as long as all other conditions stay the same they aren’t affected (equilibrium restored)

Question 14

How are Kc and Kp affected by the presence of a catalyst

Answer 14

They aren’t affected, the catalyst only causes the reaction to reach equilibrium faster