(U2) Equilibrium

Question 1

What is a reversible reaction?

Answer 1

A reaction which goes in both the forward and backward directions

Question 2

When is dynamic equilibria? (4)

Answer 2

• reversible reaction
• Where the rate of forward reaction = rate of the backward reaction
• in a closed system
• conc of reactants and products is constant

Question 3

What is equilibrium? (2)

Answer 3

• When a reversible reaction has a constant amount
• of each reactant / product

Question 4

What is a homogeneous reaction? (2)

Answer 4

• A reaction in which all the reactants and products
• are in the same physical state

Question 5

What is a heterogeneous reaction? (2)

Answer 5

• A reaction in which all the reactants and products
• are not in the same physical state

Question 6

State the equation for K_c

When can this be used?

Answer 6

• K_c = ([C]^c[D]^d) / ([A]^a[B]^b)
• for a reaction in the format:

aA + bB ⇌ cC + dD

Question 7

When is a catalyst homogenous?

Answer 7

When the catalyst is in a different phase from the reactants

Question 8

What are the conditions for the HABER process? (3)

Answer 8

• 450ºC
• 200 atm
• granulated iron catalyst

Question 9

What are the conditions for the contact process? (3)

Answer 9

• 450ºC
• 1-2 atm
• Vanadium (V) oxide catalyst

Question 10

What is the effect of increasing temperature on equilibrium

Answer 10

Moves equilibrium position toward endothermic reaction

Question 11

What is the effect of decreasing temperature on equilibrium

Answer 11

Moves equilibrium position toward exothermic reaction

Question 12

Effect of increasing pressure on equilibrium

Answer 12

Moves equilibrium position in the direction of the reaction which produces fewest moles of gas

Question 13

Effect of decreasing pressure on equilibrium

Answer 13

Moves equilibrium position in the direction of the reaction which produces most moles of gas

Question 14

What is the effect of a catalyst on equilibrium (3)

Answer 14

• Speeds forward and reverse reaction equally,
• equilibrium position does not change,
• equilibrium is reached more quickly

Question 15

Effect of increasing concentration on equilibrium

Answer 15

Moves equilibrium position in the direction of the reaction which produces fewest moles

Question 16

Effect of decreasing concentration on equilibrium

Answer 16

Moves equilibrium position in the direction of the reaction which produces most moles

Question 17

How does the value of Kc relate to the position of equilibrium?

Answer 17

• Kc > 1 = larger proportion of products —> more forward reaction —> equilibrium shifted right
• Kc < 1 = larger proportion of reactants —> more reverse reaction —> equilibrium shifted left