C6 Equilibrium Flashcards
What is Dynamic equilibrium?
The rate of the forward reaction is equal to the rate of the backwards reaction
What is an essential condition for equilbrium to occur?
It can only occur in a closed system where reactants and products cannot escape
State Le Chatelliers principle?
If a reaction at equilibrium is subjected to a change in pressure, temperature or concentration the position of equilibrium will shift to counteract the change
State the reaction that produces ethanol
C2H4 (g) + H2O (g) ⇌ C2H5OH (g) ΔH = -46kj/mol-1
What conditions are needed for the reaction of ethanol to occur?
Pressure at 60atmp
Temperature at 300 degrees celsius
Catalyst H3PO4
In accordance to the reaction how can we change temperature to increase yield of ethanol?
We can increase yield of ethanol by decreasing the temperature as it would favour the exothermic reaction. The forward reaction is exothermic so more ethanol will be produced
What is the compromise of using a low temperature like 300 degrees celsius for the reaction of ethanol?
lower temperature means a lower rate of reaction so 300 degrees is a compromise between yield and rate
In accordance to the reaction how can we change pressure to increase yield of ethanol?
By increasing the pressure it will the favour the side with fewer number of moles to restablish equilibrium so more ethanol is produced increasing rate
What is the compromise with using high pressure in reactions?
High pressure environments are expensive due to more expensive equipment needing to be used so a compromise is done between yield/speed and cost
What effect does a catalyst have on the position of equilibrium?
No effect as it only speeds up the rate in which equilibrium is established
What condition affects the value of Kc?
Temperature
For the reaction below deduce an expression for Kc
2[A] + 3[B] + [C] ⇌ [D]+ 4[E]
Kc= [D][E]4/[A]2[B]3[C]
What is the equation for Kc?
Kc= Products/reactants
What type of system is Kc relevant for?
Homogeneous systems in equilibrium
What effect does decreasing the temperature in an endothermic reaction have on Kc?
Kc decreases
What effect does increasing the temperature in an endothermic reaction have on Kc?
Kc increases
What effect does decreasing the temperature in an exothermic reaction have on Kc?
Kc increases
What effect does increasing the temperature in an exothermic reaction have on Kc?
Kc decreases
What does a catalyst do the forward and backward reaction?
Speeds up both the forward and backward reaction equally
CH4( g) + H2O( g) ⇌ CO( g) + 3 H2( g) ΔH = +210KJj/mol-1
What effect would increasing the temperature have on the position of equilibrium?
The equilibrium position shifts to the right because the forward reaction is endothermic yield of hydrogen increases
CH4( g) + H2O( g) ⇌ CO( g) + 3 H2( g) ΔH = +210KJj/mol-1
What effect would increasing the pressure have on the position of equilibrium?
The equilibrium position shifts to the left because the forward reactions produces more moles of gas so the yield of hydrogen increases
CH4( g) + H2O( g) ⇌ CO( g) + 3 H2( g) ΔH = +210KJj/mol-1
Suggest and explain why an industrial chemist may use a high pressure for this production of hydrogen from above reaction?
The high pressure increase collision frequency increasing rate of reaction.
This is a compromise pressure between an economically viable rate of reaction and a slightly lower yield of hydrogen
