Equilibria Flashcards
The reaction is done at a temperature of 800 °C, low pressure and with the presence of a nickel catalyst. Why are these conditions used? (ΔH = +206)
- Catalyst has no effect on yield. Adding a catalyst allows for a lower temperature to be used. Thus, the cost is lowered.
- Equilibrium shifts to the side with more moles of gas. This lower pressure increases the yield.
- Reaction is endothermic. Higher temperature increases yield. But high temperature is costly so a compromise temperature is used.
CO(g) + 2H2(g) ⇌ CH3OH(g)
State and explain the effect of using a catalyst on the yield of methanol in this equilibrium.
No effect on yield. Catalyst increases the rate of the forward and backward reaction equally.
What state are reversible reactions in?
A dynamic equilibrium state.
What does dynamic mean?
Both forward and backward reactions occur simultaneously.
Two features of dynamic equilibrium?
Forward and backwards reactions both occur at the same rate in a closed system.
The concentrations of the products and reactants stay constant.
Define Le Chatelier’s Principle.
If an external condition is changed, the equilibrium will shift to oppose this change.
What happens to the position of the equilibrium when temperature is increased?
It moves to the endothermic direction to try to reduce the temperature by absorbing heat.
What happens to the position of the equilibrium when temperature is decreased?
It moves to the exothermic reaction to try to increase the temperature by giving out heat.
What kind of yield is given with low temperature?
Higher yield but there’s a slow rate of reaction so a compromise temperature is usually used which gives a reasonable yield and reasonable rate of reaction.
What happens to the position of the equilibrium when pressure is increased?
Equilibrium will shift to the side with fewer moles of gas to oppose the change. Thus pressure is reduced.
What happens to the position of the equilibrium when pressure is decreased?
Equilibrium will shift to the side with more moles of gas to oppose the change and increase pressure.
What happens if the number of moles of gas is the same on both sides?
Changing pressure will have no effect on the position of equilibrium.
What kind of yield is given with increasing pressure?
Higher yield of product and will produce at a faster rate. High pressures are expensive as there are high energy costs and the equipment is also expensive.
What effect does a catalyst have on equilibrium?
No effect on the position of equilibrium but it will speed up rate at which equilibrium is achieved.
Why doesn’t a catalyst affect the position of equilibrium?
It speeds up the rate of the forwards and backwards reaction equally.
What is meant by carbon neutral?
An activity that has no net annual carbon emissions to the atmosphere.
What is Kc affected by?
Temperature only.
What does a larger Kc mean?
The greater the amount of products.
What does a smaller Kc mean?
Equilibrium favours the reactants.
