1.6 Chemical equilibria Flashcards
Define the term dynamic equilibrium
The rate of forward reaction is equal to the rate of the reverse reaction
Give an essential condition for an equilibrium mixture
Equilibrium occurs in a closed system
State le chatelier’s principle
If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance
In the equation CH4(g) + H2O(g) -> CO(g) + 3H2(g)
+210 kjmol-1
What effect would increasing the temperature have on the position of the equilibrium
Equilibrium shifts to the right
(forward reaction is endothermic, yield of hydrogen increases)
In the equation CH4(g) + H2O(g) -> CO(g) + 3H2(g)
+210 kjmol-1
What effect would increasing the pressure have on the position of the equilibrium
Equilibrium shifts to the left
(because right has more moles of gas, yield of hydrogen decreases)
CH4(g) + H2O(g) -> CO(g) + 3H2(g)
+210 kjmol-1
Suggest and explain why an industrial chemist may use a high pressure for this production of hydrogen from the above reaction
High pressure increases the collision frequency increasing the rate of reaction
This is a compromise pressure between an economically viable rate of reaction and a slightly lower yield of hydrogen
What effect does a catalyst have on the position of equilibrium
No effect
(affects the rate of forward and reverse reactions equally)
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]
Top: [D][E]^4
Bottom: [A]^2[B]^3[C]
What type of system is J=Kc relevant for
Homogenous systems in equilibrium
What does Kc being greater or lesser than 1 suggest for the position of equilibrium
Greater than 1 = over to the right
Less than 1 = over to the left
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
