Equilibrium Constant (Kp) for Homogeneous Systems (AQA A Level Chemistry): Exam Questions

When dinitrogen tetroxide gas is heated, it dissociates into nitrogen dioxide gas:

N₂O₄ (g)  ⇌  2NO₂ (g)

At a particular temperature, the equilibrium partial pressure of nitrogen dioxide was 0.67 kPa and dinitrogen tetroxide was 0.33 kPa.

What is the numerical value of K_p at this temperature?

When 5.00 mol of A reacts with 5.00 moles of B in a sealed vessel of volume 1 dm³ and total pressure of 1.5 kPa an equilibrium is established which contains 3.00 moles of C. 

A + B ⇌ 2C

What is the equilibrium partial pressure of A? 

The temperature is increased on the following gaseous equilibrium

2SO₂ (g) + O₂ (g) ⇌ 2SO₃ (g)        ΔH = -197 kJ mol^-1

Which of the following is true?

At 80 ^oC, the following equilibrium is established:

N₂ (g)   +  3H₂ (g)    ⇌   2NH₃ (g)

The partial pressures of the nitrogen, hydrogen and ammonia are 0.25 kPa, 0.80 kPa and 0.35 kPa respectively.

What is the numerical value of K_p at 80 ^oC?

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

CO (g) + 2H₂ (g) ⇋ CH₃OH (g)

Thermodynamic data for the components of this equilibrium are:

This equilibrium occurs at a temperature of 585 K, a total pressure of 45.0 MPa and in a 1.80 dm³ vessel.

At equilibrium, the vessel contains 0.0400 mol of CO (g), 0.0800 mol of H₂ (g) and 0.0450 mol of CH₃OH (g).

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

9.20 g of dinitrogen tetroxide, N₂O₄ (g), was heated to a temperature of 350 K at a pressure of 13.5 kPa and dissociated into nitrogen dioxide, NO₂ (g).

N₂O₄ (g)   ⇌   2NO₂ (g)

At equilibrium, 70 % of N₂O₄ (g) had dissociated.

What is the numerical value of K_p at 350 K?

3.00 moles of SO₃ (g) are placed into a 8 dm³ container and heated to 1200 K.

2SO₃ (g) ⇌ 2SO₂ (g) + O₂ (g)

At equilibrium, the mixture contained 0.58 moles of oxygen at a total pressure 3.45 x 10⁶ Pa.

What is the value for K_p?

Methanol can be produced by a multi-step process using methane and water as the starting materials. The first step is the production of synthesis gas, which is a mixture of carbon monoxide and hydrogen that is used to synthesise many chemicals including methanol.

 CH₄ (g) + H₂O (g) ⇋ CO (g) + 3H₂ (g)      ∆H = +206 kJ mol^-1

Which of the following changes would increase the value of K_p for this equilibrium?

Chloromethane can be made from the following reaction. 0.80 moles of methanol and hydrogen chloride are added to the reaction container.

 CH₃OH (g) + HCl (g) ⇌ CH₃Cl (g) + H₂O (g)

 At 120 ℃, the value for K_p is 6.00 x 10³  

Which statement about the number of moles of reactants and products at equilibrium is correct?

What are possible K_p units for the decomposition of calcium carbonate?