Physical 1 Section 1 - Unit 6: Equilibria
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State how an increase in pressure would change the position of the equilibrium and the value of the equilibrium constant for this reaction (2 marks)
• Equilibrium position: displaced to the right - Equilibrium constant: no change
Explain the term homogeneous (1 mark)
• All reactants in the same phase or state
Explain the term dynamic equilibrium (1 mark)
• Forward and backward reactions occur at the same rate - So there is no change in the proportions of reactants and products
Explain the term equilibrium (1 mark)
• Concentrations of reactants and products are constant OR • Rates of forward and backward reactions equal
What effect would increasing temperature have on the yield of ammonia? (5 marks)
• Equilibrium will shift towards the left • To oppose this • Move in the endothermic, backwards direction • To decrease the temperature • Giving a lower yield of ammonia
State le Chatelier’s principle (1 mark)
• If any factor is changed which affects an equilibrium, the equilibrium will shift to counteract the change
State the effect, if any, of a catalyst on the time taken to reach equilibrium (1 mark)
• Time decreases
State the effect, if any, of a catalyst on the position of an equilibrium (1 mark)
• No effect
Explain, in terms of the behaviour of particles, why a high operating pressure is used in industry (2 marks)
• The reaction gets to equilibrium faster • Higher pressure leads to higher concentration of particles • So more collisions in a given time
State what the effect is of increasing pressure on the yield of methanol (5 mark)
• Equilibrium will shift to oppose this • Move towards the side with fewer moles of gas to try to reduce the pressure • Position of equilibrium will shift towards the right • Because there are 3 moles of gas on the left but only 1 mole of gas on the right • Giving a higher yield of methanol
Explain the general effect of increasing pressure on the yield produced (3 marks)
• Equilibrium will shift to oppose this • Move towards the side with fewer moles of gas to reduce the pressure • Therefore reducing the yield produced
State the equation for the Haber process (1 mark)
N2 + 3H2 ⇌ 2NH3
State the temperature, pressure and catalyst needed for the Haber process (3 marks)
• Temperature: 450°C • Pressure: 200 – 1000 atm • Catalyst: Iron