Factors Affecting Equilibrium

Chemistry

For an endothermic reaction, what is the sign of ΔH, where does energy appear in the equation, and how does increasing temperature shift the position?

ΔH is positive, energy is a reactant, and increasing temperature shifts the position forward

For an exothermic reaction, what is the sign of ΔH, where does energy appear in the equation, and how does increasing temperature shift the position?

ΔH is negative, energy is a product, and increasing temperature shifts the position backward

An exothermic equilibrium has it temperature decreased. How does the position shift and why?

Shifts forward, so the reaction releases energy

N₂(g) + 3H₂(g) ⇋ 2NH₃(g), ΔH = −92 kJ mol⁻¹. How does increasing temperature affect the position and the amount of NH₃?

Shifts backward, less NH₃ at the new equilibrium

If the forward reaction has ΔH of -92 kJ mol^-1 what is ΔH for the reverse reaction?

92 kJ mol^-1

Use collision theory to explain why increasing temperature shifts the position in the endothermic direction.

Both rates increase, but the endothermic direction increases more, so the position shifts that way until rates are equal again

Use collision theory to explain the effect of adding more reactant (increasing concentration) to an equilibrium system

Forward rate increases (more frequent collision), position shifts forward until rates are equal again

Use collision theory to explain what happens when a product is removed (concentration decreased) from an equilibrium system

The reverse rate decreases (fewer collisions), so the position shifts forward

The volume of a gaseous equilibrium system is decreased (pressure increased). What happens to the concentrations and the position of equilibrium?

Concentration increases, the position shifts toward the side with fewer moles of gas

H₂(g) + I₂(g) ⇋ 2HI(g). The volume is decreased. What is the effect on the position of equilibrium?

Pressure increases, concentration increases, however there is an equal number of gas particles on each side, so rates change equally and there is no shift

Pressure in a fixed-volume gaseous equilibrium is increased by adding extra reactant gas. Predict the shift in positon.

The position will shift forward

What does Boyle’s law say about pressure and volume in a variable-volume system?

Pressure and volume are inversely proportional. Decreasing volume increases pressure and concentration.

What happens to the position of an aqueous equilibrium when it is diluted with water? Apply to Fe³⁺(aq) + SCN⁻(aq) ⇋ FeSCN²⁺(aq)

Lowers all aqueous concentrations. The system will shift towards the side with more dissolved particles

Le Chatalier’s Principle

If a system at equilibrium is changed, it adjusts to partially oppose the change until equilibrium is re-established