Equilibria (3.1.6-Phys.) Flashcards
Define dynamic equilibria
1) Forward and backward reactions occur at the same rate
2) The concentration of all reactants and products are constant
State Le Chatalier’s principle
If a closed system at equilibrium is subject to a change, the position of equilibrium shifts to oppose the change.
Define homogeneous
All reactants and products in the same phase
The Contact Process:
2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
What happens to the yield when you increase pressure?
The system will oppose this change by shifting the position of equilibrium in the forward direction, as there are fewer moles of gas. Therefore the yield increases.
The Contact Process:
2SO₂(g) + O₂(g) ⇌ 2SO₃(g) (exothermic)
What happens to the yield when you increase temperature?
The system will oppose the increase in temperature by shifting the position of equilibrium in the backward direction because the endothermic direction. Therefore the yield decreases.
Compromise temperature for…
2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
Rate: increases
Yield: decreases
Compromise: medium temperature- acceptable yield and fast rate
Compromise pressure for…
2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
Rate: Increases
Yield: increases
Compromises: medium pressure, because high pressure equipment is expensive to build and maintain
Kc expression for the reaction A + B —–> C + 2D
[C] x [D]² / [A] x [B]
Units of [X] =?
mol dm⁻³
What is the only factor that affects Kc?
A change in temperature
How do you calculate Kc with a given volume (v)?
[mol of C/v] x [mol of D/v] / [mol of A/v] x [mol of B/vol]
What is the effect of a catalyst on a system at equilibrium?
No effect because the catalyst increases the rate of reaction in both the forward and backward reactions equally.
