Predicting if a Reaction is in Equilibrium Trial Keq Lesson 9
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Transcript of Predicting if a Reaction is in Equilibrium Trial Keq Lesson 9
Predicting if a Reaction is in Equilibrium
Trial Keq
Lesson 9
The Keq is a constant- a number that does not change.
Changing the volume, pressure, or any concentration, does not change the Keq.
Only temperature changes the Keq
If the [Reactant] is increased the reaction will shift
The Keq is a constant- a number that does not change.
Changing the volume, pressure, or any concentration, does not change the Keq.
Only temperature changes the Keq
If the [Reactant] is increased the reaction will shift rightThe Keq will
The Keq is a constant- a number that does not change.
Changing the volume, pressure, or any concentration, does not change the Keq.
Only temperature changes the Keq
If the [Reactant] is increased the reaction will shift rightThe Keq will remain constant
If the temperature of an endothermic reaction is increased the reaction will
The Keq is a constant- a number that does not change.
Changing the volume, pressure, or any concentration, does not change the Keq.
Only temperature changes the Keq
If the [Reactant] is increased the reaction will shift rightThe Keq will remain constant
If the temperature of an endothermic reaction is increased the reaction will shift rightThe Keq will
The Keq is a constant- a number that does not change.
Changing the volume, pressure, or any concentration, does not change the Keq.
Only temperature changes the Keq
If the [Reactant] is increased the reaction will shift rightThe Keq will remain constant
If the temperature of an endothermic reaction is increased the reaction will shift rightThe Keq will increase
1. If 6.00 moles CO2, and 6.00 moles H2 are put in a 2.00 L
container at 670 oC, calculate all equilibrium concentrations.
CO(g) + H2O(g) ⇄ CO2(g) + H2(g) Keq = 9.0
Initial concentrations means ICE!Because we are starting with products it goes leftAdd on left and subtract on right
I 0 0 3.00 M 3.00 M
C +x +x -x -x
E x x 3.00 - x 3.00 - x
Keq = [CO2][H2] = 9.0
[CO][H2O]
Keq = (3 - x)2 = 9 x2
Square root both sides
3 - x = 3 x 1
Cross multiply
3x = 3 - x
4x = 3
[CO] = [H2O] = x = 0.75 M
[CO2] = [H2] = 3.00 - 0.75 = 2.25 M
Ktrial How can you tell if a system is in equilibrium or not? Calculate a trial Keq. Put the concentrations into the equilibrium expression and evaluate.
Ktrial How can you tell if a system is in equilibrium or not? Calculate a trial Keq. Put the concentrations into the equilibrium expression and evaluate. If Ktrial = Keq Equilibrium
Keq
Kt
Ktrial How can you tell if a system is in equilibrium or not? Calculate a trial Keq. Put the concentrations into the equilibrium expression and evaluate. If Ktrial = Keq Equilibrium If Ktrial < Keq Not at Equilibrium
KeqKt
Ktrial How can you tell if a system is in equilibrium or not? Calculate a trial Keq. Put the concentrations into the equilibrium expression and evaluate. If Ktrial = Keq Equilibrium If Ktrial < Keq Not at Equilibrium Shifts Right
KeqKt
Ktrial How can you tell if a system is in equilibrium or not? Calculate a trial Keq. Put the concentrations into the equilibrium expression and evaluate. If Ktrial = Keq Equilibrium If Ktrial < Keq Not at Equilibrium Shifts Right If Ktrial > Keq
Keq Kt
Ktrial How can you tell if a system is in equilibrium or not? Calculate a trial Keq. Put the concentrations into the equilibrium expression and evaluate. If Ktrial = Keq Equilibrium If Ktrial < Keq Not at Equilibrium Shifts Right If Ktrial > Keq Not at Equilibrium Shifts Left
Keq Kt
The following amounts of gases are placed into a 2.0 L container. Determine if each system is at equilibrium or not. If not, determine the direction that the equilibrium will shift in order to get to equilibrium.
2NH3(g) ⇄ N2(g) + 3H2(g) Keq = 10
1. 2.0 moles NH32.0 moles N2 2.0 mole H2
Get concentrations.
1.0 M 1.0 M 1.0 MCalculate Kt
Kt = [N2][H2]3 = (1)(1)3 = 1
[NH3]2 (1)2
Not in equilibrium Kt < Keq Shifts right!
The following amounts of gases are placed into a 2.0 L container. Determine if each system is at equilibrium or not. If not, determine the direction that the equilibrium will shift in order to get to equilibrium.
2NH3(g) ⇄ N2(g) + 3H2(g) Keq = 10
2. 2.0 moles NH34.0 moles N2 4.0 mole H2
Get concentrations.
1.0 M 2.0 M 2.0 MCalculate Kt
Kt = [N2][H2]3 = (2)(2)3 = 16
[NH3]2 (1)2
Not in equilibrium Kt > Keq Shifts left!
The following amounts of gases are placed into a 2.0 L container. Determine if each system is at equilibrium or not. If not, determine the direction that the equilibrium will shift in order to get to equilibrium.
2NH3(g) ⇄ N2(g) + 3H2(g) Keq = 10
3. 2.0 moles NH32.5 moles N2 4.0 mole H2
Get concentrations.
1.0 M 1.25 M 2.0 MCalculate Kt
Kt = [N2][H2]3 = (1.25)(2)3 = 10
[NH3]2 (1)2
In equilibrium Kt = Keq
4. If 4.00 moles of CO, 4.00 moles H2O, 6.00 moles CO2, and
6.00 moles H2 are placed in a 2.00 L container at 670 oC,
Keq = 1.0CO(g) + H2O(g) ⇄ CO2(g) + H2(g)
Is the system at equilibrium?If not, how will it shift in order to get there?Calculate all equilibrium concentrations.
Get Molarities
2.00 M 2.00 M 3.00 M 3.00 M
Calculate a Kt
Kt = (3)(3) = 2.25(2)(2)
Not in equilibrium Shifts left!
Do an ICE chart
CO(g) + H2O(g) ⇄ CO2(g) + H2(g)
I 2.00 M 2.00 M 3.00 M 3.00 MC +x +x -x -xE 2.00 + x 2.00 + x 3.00 - x 3.00 - x
Keq = (3 - x)2 = 1.0(2 + x)2
Square root3 - x = 1.02 + x 3 - x = 2 + x1 = 2xx = 0.50 M
[CO2] = [H2] = 3.00 - 0.50 = 2.50 M
[CO] = [H2O] = 2.00 + 0.50 = 2.50 M
Size of the Keq
Big Keq
Keq =
Keq = 10
products
reactants
Little Keq-
Keq =
Keq = 0.1
Note that the keq cannot be a negative number!
products
reactants
Keq about 1
Keq =
Keq = 1
products
reactants
Which reaction favours the products the most? Keq = 2.6 x 106
Keq = 3.5 x 102
Which reaction favours the reactants the most? Keq = 2.6 x 10-6
Keq = 3.5 x 10-7
Which reaction favours the products the most? Keq = 2.6 x 106
Keq = 3.5 x 102
Which reaction favours the reactants the most? Keq = 2.6 x 10-6
Keq = 3.5 x 10-7