3.1.10 Equilibrium constant (A-level only)

An equilibrium mixture is prepared in a container of fixed volume.

CO(g) + Cl₂(g) ⇌ COCl₂(g)

ΔH = −108 kJ mol⁻¹

The temperature of this mixture is decreased and the mixture is allowed to reach a new equilibrium.

Which is greater for the new equilibrium than for the original equilibrium?

• The mole fraction of carbon monoxide

• The partial pressure of chlorine

• The total pressure of the mixture

• The value of the equilibrium constant, K_p

Tags

NGSS.HS-PS1-5

Which statement about K_p is correct for this reaction in the gas phase?

W + X + Y₂ ⇌ WXY + Y

ΔH = −46 kJ mol⁻¹

• The value of K_p is independent of pressure.

• The value of K_p increases as pressure increases.

• The value of K_p increases as temperature increases.

• The value of K_p is independent of temperature.

Which change would alter the value of the equilibrium constant (K_p) for this reaction?

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

• Increasing the total pressure of the system.

• Increasing the concentration of sulfur trioxide.

• Increasing the concentration of sulfur dioxide.

• Increasing the temperature

Tags

NGSS.HS-PS1-5

NGSS.HS-PS1-6

This question is about the reaction given below.

CO(g) + H₂O(g) ⇌ CO₂(g) + H₂(g)

Enthalpy data for the reacting species are given in the table below.

Which one of the following statements is not correct?

• The value of K_p changes when the temperature changes.

• The activation energy decreases when the temperature is increased.

• The entropy change is more positive when the water is liquid rather than gaseous.

• The enthalpy change is more positive when the water is liquid rather than gaseous.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-5

The equation for the combustion of butane in oxygen is

C₄H₁₀ + 6.5O₂ → 4CO₂ + 5H₂O

The mole fraction of butane in a mixture of butane and oxygen with the minimum amount of oxygen required for complete combustion is

• 0.133

• 0.153

• 0.167

• 0.200

This question relates to the equilibrium gas-phase synthesis of sulphur trioxide:

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

Thermodynamic data for the components of this equilibrium are given.

This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm³. At equilibrium, the vessel contains 0.0500 mol of SO₂(g), 0.0800 mol of O₂(g) and 0.0700 mol of SO₃(g).

The mole fraction of SO₃ in the equilibrium mixture is

• 0.250

• 0.350

• 0.440

• 0.700

Tags

NGSS.HS-PS1-4

This question relates to the equilibrium gas-phase synthesis of sulphur trioxide:

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

Thermodynamic data for the components of this equilibrium are given.

This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm³. At equilibrium, the vessel contains 0.0500 mol of SO₂(g), 0.0800 mol of O₂(g) and 0.0700 mol of SO₃(g).

With pressures expressed in MPa units, the value of the equilibrium constant, K_p, is

• 4.90

• 6.48

• 9.07

• 16.8

Tags

NGSS.HS-PS1-4

This question relates to the equilibrium gas-phase synthesis of sulphur trioxide:

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

Thermodynamic data for the components of this equilibrium are given.

This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm³. At equilibrium, the vessel contains 0.0500 mol of SO₂(g), 0.0800 mol of O₂(g) and 0.0700 mol of SO₃(g).

Possible units for the equilibrium constant Kp include

• no units

• kPa

• Mpa⁻¹

• kPa⁻²

This question relates to the equilibrium gas-phase synthesis of sulphur trioxide:

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

Thermodynamic data for the components of this equilibrium are given.

This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm³. At equilibrium, the vessel contains 0.0500 mol of SO₂(g), 0.0800 mol of O₂(g) and 0.0700 mol of SO₃(g).

At equilibrium in the same vessel of volume 1.80 dm³ under altered conditions, the reaction mixture contains 0.0700 mol of SO₃(g), 0.0500 mol of SO₂(g) and 0.0900 mol of O₂(g) at a total pressure of 623 kPa. The temperature in the equilibrium vessel is

• 307 °C

• 596 K

• 337 °C

• 642 K

Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-5

The following information concerns the equilibrium gas-phase synthesis of methanol.

CO(g) + 2H₂(g) ⇌ CH₃OH(g)

At equilibrium, when the temperature is 68 °C, the total pressure is 1.70 MPa.The number of moles of CO, H2 and CH3OH present are 0.160, 0.320 and 0.180, respectively. Thermodynamic data are given.

Possible units for the equilibrium constant, K_p, for this reaction are

• no units

• kPa

• MPa⁻¹

• kPa⁻²

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4