Sulfur trioxide decomposes on heating to form an equilibrium mixture containing sulfur dioxide and oxygen.

2SO_3(g) ⇌ 2SO_2(g) + O_2(g)

A sample of sulfur trioxide was heated and allowed to reach equilibrium at 1,050 K. 

The equilibrium mixture contained 12.8 g of oxygen.

Calculate the mass, in g, of sulfur dioxide in the equilibrium mixture.

Give your answer to 3 significant figures.

The amounts of each substance in the equilibrium mixture are shown in the table below.

Calculate the mole fraction of each gas at equilibrium.

For this reaction at 1,050 K, the total pressure is 1.91 x 10⁵ Pa.

Write the expression for K_p.

Use the answers to parts b) and c) to calculate the equilibrium constant, K_p for this reaction.

Give your answer to 3 significant figures and give the units, if any, of K_p.

In the manufacture of sulfuric acid, sulfur dioxide, SO₂, is oxidised to sulfur trioxide, SO₃, as shown by the equilibrium below.

2SO_2(g) + O_2(g) ⇌ 2SO_3(g)    ΔH = -197 kJ mol^-1

A scientist fills a 12.6 dm³ vessel with O_2(g) at room temperature and pressure, and then adds 21.2 g of sulfur dioxide. 

The scientist adds a V₂O₅ catalyst and heats the mixture. The mixture is allowed to reach equilbrium at a pressure of 250 kPa and a temperature of 800°C.

The equilibrium mixture was found to contain 0.176 moles of SO₃. 

Calculate the value of K_p for this equilibrium at 800°C.

Give your answer to 3 significant figures and give the units of K_p.

Explain the significance of expression K_p ≪ 1.

The scientist repeats the reaction but at a lower temperature. The mixture is allowed to reach equilibrium.

Explain the effect, if any, on the value of K_p. 

Nitrogen monoxide, NO, and oxygen, O₂, react to form nitrogen dioxide, NO_2,as shown by the equilibrium below.

2NO_(g) + O_2(g) ⇌ 2NO_2(g)

Write an expression for K_c for this equilibrium and state the units.

Nitrogen and oxygen gases were mixed together and pressurised so that their total gas volume is 6.0 dm³.

The mixture is allowed to reach equilibrium at constant volume and temperature. 

The equilibrium mixture contains 0.48 mol NO and 0.96 mol O₂.

K_c = 38 mol^-1 dm³.

Calculate the amount, in mol, of NO₂ in the equilibrium mixture.

Give your answer to 2 significant figures.

The table below shows the values of K_p for this equilibrium at 298 K and at 500 K.

Explain how information in the table above can be used to deduce that the forward reaction is exothermic.

The pressure of the equilibrium mixture is increased at the same temperature.

Explain, in terms of K_p, how you would expect the equilbrium position to move and change. 

Methanol can be manufactured in a reversible reaction as shown below.

CO_(g) + 2H_2(g) ⇌ CH₃OH_(g)

The graph below shows how the partial pressures of each gas change with time at a constant temperature.

Draw a cross (x) on the appropriate axis of the graph when the mixture reaches equilibrium.

A 0.35 mol sample of carbon monoxide is mixed with hydrogen in a 1 : 2 mol ratio and allowed to reach equilibrium in a sealed flask at a constant temperature.

At equilibrium the mixture contains 0.16 mol of methanol.

The total pressure of this mixture is 8.5 x 10⁴ kPa.

Calculate the partial pressure, in kPa, of hydrogen in the equilibrium mixture.

Give your answer to 2 significant figures.

Some more carbon monoxide is added to the mixture and the temperature remains unchanged. The new mixture is allowed to reach equilibrium.

State the effect, if any, on the partial pressure of methanol and on the value of K_p.

A catalyst is added to this mixture at equilbrium. 

State the effect, if any, on the value of K_p for this equilibrium.

Explain your answer.

Ammonia, NH₃, is manufactured by the Haber process from nitrogen and hydrogen, as shown below.

N_2(g) + 3H_2(g) ⇌ 2NH_3(g)     ΔH = -92 kJ mol^-1

At 298 K, the free energy change, ΔG, for the production of ammonia is -33.2 kJ mol^-1. 

ΔG is linked to K_p by the equation: 

ΔG = -RTlnK_p

The gas constant, R = 8.31 J K^-1 mol^-1

T = temperature in K

Calculate K_p for this equilibrium at 298 K.

Give your answer to 3 significant figures.

Explain, in terms of K_p, the effect of an increase in temperature on the equilibrium position of this reaction.

15.0 moles of nitrogen was mixed with 20.0 moles of hydrogen. The container was sealed and the contents allowed to reach equilibrium at a temperature of 500 K. The equilibrium mixture formed contained 2.60 moles of ammonia.

Calculate the mole fractions of nitrogen and hydrogen in the equilibrium mixture.

Give your answers to 3 significant figures.

At 500 K, the value of K_p for this equilibrium is 3.60 x 10^-2 kPa^-2. 

Using your answer to part c), calculate the total pressure, in kPa, of the container.

Give your answer to 3 significant figures.

This reaction is repeated with the same starting amounts of nitrogen and hydrogen. The same temperature is used but the container has a smaller volume.

State the effects, if any, of this change on the yield of ammonia and on the value of K_p.

The Haber process is used in industry to produce ammonia from nitrogen and hydrogen.

N_2(g) + 3H_2(g)  ⇌  2NH_3(g)    ΔH = -92 kJ mol^-1

At a pressure of 2.00 x 10⁷ Pa, 1.00 moles of N_2(g) is mixed with 3.00 moles of H_2(g). The mixture was left to reach equilibrium and was found to contain 0.300 moles of NH_3(g).

Calculate the number of moles of N_2(g) and H_2(g) in the equilibrium mixture.

Calculate the partial pressure of NH₃ in this equilibrium mixture.

In a different equilibrium mixture, the partial pressures of each substance are those shown in the table below.

Calculate the value of the equilibrium constant, K_p, to 3 significant figures. Include the units in your answer.

The reaction is repeated at a higher pressure.  State the effects, if any, on the equilibrium yield of NH₃ and the value of K_p.

Methanol is produced by mixing carbon monoxide with hydrogen and the mixture left to reach equilibrium.

CO_(g) + 2H_2(g)  ⇌  CH₃OH_(g)    ΔH = -91 kJ mol^-1

Write an expression for the equilibrium constant, K_p.

A mixture of 0.230 moles of CO and 0.460 moles of H₂ is left to reach equilibrium in a container which is at a pressure of 1.04 x 10⁴ kPa. The equilibrium mixture is found to contain 0.120 moles of CO.

Calculate the partial pressure of H₂ in the equilibrium mixture to three significant figures.

Some more CO is added to the mixture and allowed to reach equilibrium. State what effect this will have, if any, on the value of K_p and on the partial pressure of methanol.

State and explain the effect, if any, on the value of K_p if a catalyst was added to the reaction.