General Equilibrium

CuO(s) + H₂(g) ↔ Cu(s) + H₂O(g)

ΔH = –2.0 kilojoules mol^–1

When the substances in the equation above are at equilibrium at pressure P and temperature T, the equilibrium can be shifted to favor the products by

• increasing the pressure by means of a moving piston at constant T

• increasing the pressure by adding an inert gas such as nitrogen

• decreasing the temperature

• adding a catalyst

Tags

NGSS.HS-PS1-5

In which of the following systems would the number of moles of the substances present at equilibrium NOT be shifted by a change in the volume of the system at constant temperature?

• CO(g) + NO(g) ↔ CO₂(g) + ½ N₂(g)

• N₂(g) + 3 H₂(g) ↔ 2 NH₃(g)

• N₂(g) + 2 O₂(g) ↔ 2 NO₂(g)

• NO(g) + O₃(g) ↔ NO₂(g) + O₂(g)

PCl₃(g) + Cl₂(g) ↔ PCl₅(g) + energy

Some PCl₃ and Cl₂ are mixed in a container at 200°C and the system reaches equilibrium according to the equation above. Which of the following causes an increase in the number of moles of PCl₅ present at equilibrium?

• Decreasing the volume of the container

• Raising the temperature

• Adding a mole of He gas at constant volume

• Raising the temperature and adding a mole of He gas at constant volume

Tags

NGSS.HS-PS1-5

4 HCl(g) + O₂(g) ↔ 2 Cl₂(g) + 2 H₂O(g)

Equal numbers of moles of HCl and O₂ in a closed system are allowed to reach equilibrium as represented by the equation above. Which of the following must be true at equilibrium?

• The [HCl] must be less than [Cl₂].

• The [O₂] must be greater than [HCl].

• The [Cl₂] must equal [H₂O].

• The [O₂] must be greater than [HCl] and [Cl₂] must equal [H₂O].

Tags

NGSS.HS-PS1-7

2 SO₂(g) + O₂(g) ↔ 2 SO₃(g) When 0.40 mole of SO₂ and 0.60 mole of O₂ are placed in an evacuated 1.00-liter flask, the reaction represented above occurs. After the reactants and the product reach equilibrium and the initial temperature is restored, the flask is found to contain 0.30 mole of SO₃. Based on these results, the expression for the equilibrium constant, Kc, of the reaction is

• 
• 
• 
• 

Tags

NGSS.HS-PS1-7

2 SO₃ (g) ↔ 2 SO₂ (g) + O₂ (g)

After the equilibrium represented above is established, some pure O₂ (g) is injected into the reaction vessel at constant temperature. After equilibrium is reestablished, which of the following has a lower value compared to its value at the original equilibrium?

• Keq for the reaction.

• The total pressure in the reaction vessel.

• The amount of SO₃ (g) in the reaction vessel.

• The amount of SO₂ (g) in the reaction vessel.

Tags

NGSS.HS-PS1-6

W(g) + X(g) ↔ Y(g) + Z(g)

Gases W and X react in a closed, rigid vessel to form gases Y and Z according to the equation above. The initial pressure of W(g) is 1.20 atm and that of X(g) is 1.60 atm. No Y(g) or Z(g) is initially present. The experiment is carried out at constant temperature. What is the partial pressure of Z(g) when the partial pressure of W(g) has decreased to 1.0 atm?

• 0.20 atm

• 0.40 atm

• 1.0 atm

• 1.2 atm

Tags

NGSS.HS-PS1-5

2 NO(g) + O₂(g) ↔ 2 NO₂(g)

ΔH < 0

Which of the following changes alone would cause a decrease in the value of Keq for the reaction represented above?

• Decreasing the temperature

• Increasing the temperature

• Decreasing the volume of the reaction vessel

• Adding a catalyst

Tags

NGSS.HS-PS1-5

NGSS.HS-PS1-6

What is the equilibrium expression for:

Fe₃O₄(s) + 4 H₂(g) ↔ 3 Fe(s) + 4 H₂O(g)

• K = ([Fe]³[H₂O]⁴ ) / ([Fe₃O₄][H₂]⁴)

• K = ([Fe₃O₄][H₂]⁴)/ ([Fe]³[H₂O]⁴)

• K = [H₂O]⁴ / [H₂]⁴

• K = ([Fe][H₂O]) / ([Fe₃O₄][H₂])

Which is the reactant - and why?

• A, as its concentration decreases

• B, as its concentration decreases

• A, as its concentration increases

• B, as its concentration increases

Tags

NGSS.HS-PS1-5