Unit 3-Equilibria

Question 1

What does ⇌ mean?

Answer 1

A reversible reaction

Question 2

Why can equilibrium only be reached in a closed system?

Answer 2

Because no reactants or products can escape, so concentrations remain constant.

Question 3

Describe concentrations at equilibrium.

Answer 3

They remain constant but are rarely equal.

Question 4

Describe reaction rates at equilibrium.

Answer 4

The forward and reverse reactions occur at equal rates.

Question 5

Why shift equilibrium in industry?

Answer 5

To move the equilibrium in favour of the products and maximise yield/profit.

Question 6

Which conditions affect equilibrium position?

Answer 6

Changing concentration, temperature, or pressure.

Question 7

What happens when a system at equilibrium is changed?

Answer 7

It adjusts to oppose the change (Le Chatelier’s principle).

Question 8

Adding more Fe³⁺(aq) to
Fe³⁺(aq) + CNS^-(aq) ⇌ FeCNS²⁺(aq)

Answer 8

Equilibrium will shift to the right and make more products.

Question 9

Adding more FeCNS²⁺(aq) to

Fe³⁺(aq) + CNS^-(aq) ⇌ FeCNS²⁺(aq)

Answer 9

Equilibrium will shift to the left and make more reactants.

Question 10

N₂(g) + 3H₂ ⇌ 2NH₃(g)
ΔH_forward is negative
Which way will the equilbrium shift if the temperature is increased?

Answer 10

Shifts left (towards the endothermic direction).

Question 11

N₂(g) + 3H₂ ⇌ 2NH₃(g)
ΔH _forward is negative

Decreasing temperature

Answer 11

Shifts right (towards the exothermic direction).

Question 12

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

Explain the change in the position of equilibrium when the pressure is increased.

Answer 12

Shifts right because the product side has fewer moles of gas.

Question 13

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

Explain the change in the position of equilibrium when the pressure is decreased.

Answer 13

Shifts left because the reactant side has more moles of gas.

Question 14

Why does pressure not affect H₂(g) + I₂(g) ⇌​ 2HI(g)

Answer 14

Both sides have the same number of gas moles, so neither side is favoured.

Question 15

Effect of a catalyst on equilibrium

Answer 15

Equilibrium is reached faster, but the position of equilibrium does not change.

Question 16

Why does catalyst not affect position of equilibrium?

Answer 16

It speeds up both forward and reverse reactions equally, so neither side is favoured.