Chapter 6 (Equilibria) Flashcards
(23 cards)
What state do reversible reactions reach?
A dynamic equilibrium
What are the two features of a dynamic equilibrium?
- Forward and backward reactions occur at equal rates.
* The concentrations of reactants and products remain constant.
What does Le Chatelier’s principle state?
If an external condition changes then the equilibrium will shift to oppose the change.
What is the effect on equilibrium if temperature is increased?
The equilibrium will move in the endothermic direction to try to reduce the temperature by absorbing heat.
What is the effect on equilibrium if temperature is decreased?
The equilibrium will move in the endothermic direction to increase the temperature by releasing heat.
What is the effect on equilibrium if pressure is increased?
Equilibrium will shift towards the side with fewer moles of gas to oppose the change and decrease pressure.
What is the effect on equilibrium if pressure is decreased?
Equilibrium will shift towards the side with more moles of gas to oppose the change and increase the pressure.
What are the advantages and disadvantages of changing temperature?
Lower temperature may increase the yield but reaction may be slower.
Increasing temperature may be more expensive/require more energy.
What are the advantages and disadvantages of changing pressure?
Increasing pressure may give a higher yield and a faster rate of reaction but conditions may be expensive to produce and the stronger equipment to contain higher pressure may be expensive.
What is the effect on equilibrium if concentration is increased?
Equilibrium will shift away from the side with the increased concentration to oppose the change and decrease the concentration.
What is the effect on equilibrium if concentration is decreased?
Equilibrium will shift towards the side with the decreased concentration to oppose the change and increase the concentration.
What is the effect on equilibrium if a catalyst is added?
No effect on the position of the equilibrium but will increase the rate that equilibrium is reached.
(Will lower the activation energy so lower energy costs)
What is the equation for producing ethanol from the hydration of ethene?
CH2=CH2 (g) + H2O (g) ⇌ CH3CH2OH(l)
What are the conditions for the production of methanol from the hydration of ethene and why are these conditions used?
Temperature = 300º Pressure = 70 atm Catalyst = Concentrated H3PO4
Low temperature gives a good yield but a slow rate
High pressure gives a high yield and a high rate. Too high a pressure would lead to high energy cost for pumps to produce the pressure. High pressure also leads to unwanted polymerisation of ethene to poly(ethene).
Define carbon neutral
An activity that has no net annual carbon emissions to the atmosphere.
What is the equation for the production of methanol from CO?
CO(g) + 2H2(g) ⇌ CH3OH(g)
What are the conditions for the production of methanol from the Carbon Monoxide and why are these conditions used?
Temperature = 400º Pressure = 50 atm Catalyst = Chromium and Zinc Oxide
Low temperature gives good yield but slow rate.
High pressure gives a good yield and high rate. Too high pressure would lead to too high energy costs for pumps to produce the pressure.
What is the equation for the Haber Process?
N2 + 3H2 ⇌ 2NH3
What are the conditions for the Haber Process and why are these used?
Temperature = 450º Pressure = 200 - 1000atm Catalyst = Iron
Low temperature gives good yield but slow rate.
High pressure gives a good yield and high rate. Too high pressure would lead to too high energy costs for pumps to produce the pressure.
What are the two equations that lead to the production of Sulphur Trioxide?
1) S(s) + O2(g) > SO2(g)
2) SO2(g) + 1/2O2(g) ⇌ SO3(g)
What are the conditions for the production of Sulphur Trioxide and why are they used?
Temperature = 450º Pressure = 1 or 2 atm Catalyst = V2O5
Low temp gives good yield but slow rate: compromise moderate temp used
High pressure only gives slightly better yield and high rate: too high a pressure would lead to too high energy costs for pumps to produce the pressure
Which factor changes Kc?
Temperature
What can Kc show?
The larger the Kc then the greater the amount of products, the smaller the Kc then the reactants are favoured.
