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Excelet
Using "Solver" to Solve Equilibrium Calculations
Objective: To be able to easily solve higher-order polynomials
Beware of the behavior of polynomials and the number of roots or solutions!
In chemistry, there is only one correct root for an equilibrium problem!!!
So before using the Solver, get the solution via guessing close to the value.
If you play long enough you will get the value of x by guessing!!!
To use this Excelet, Solver must be loaded in Excel.
Click on the tabs to navigate!!!
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Haber Process Equilibrium
guess
(N2)eq x = K = 4.34E-03
This is a quartic equation! (N2)o= 1 K = (NH3)2/(N2)(H2)
3
initial concentrations
(H2)o= 1
left-side right-side
0.00434
equilibrium concentrations:
(N2)eq= ICE chart
(H2)eq=
(NH3)eq=
calculated K =
from equilbrium concentrations
The formulas on this wooksheet only have named variables!
Sinex 2008
2 2 3
2
3
3
2 2
2
3
2 o 2 o
N + 3H 2NH
(NH )K =
(N )(H )
(2x)K =(N ) - x (H ) - 3x
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Sulfur Oxides Equilibrium
guess
(SO3)eq x = K = 5
This is a cubic equation! (SO2)o= 1 K = (NH3)2/(N2)(H2)
3
initial concentrations
(O2)o= 1
left-side right-side
5
equilibrium concentrations:
(SO2)eq= ICE chart
(O2)eq=
(SO3)eq=
calculated K =
from equilbrium concentrations
Sinex 2008
2 2 3
2
3
2
2 2
2
2
2 o 2 o
2SO + O 2SO
(SO )K =
(SO ) (O )
(x)K =(SO ) - x (O ) - 0.5x
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Decomposition of PCl5
guess
(PCl3)eq= (Cl2)eq x = K = 4.0E-03
This is a quadratic equation! initial concentration (PCl5)o= 0.5
left-side right-side
0.004
equilibrium concentrations:
(PCl5)eq= ICE chart
(PCl3)eq=
(Cl2)eq=
calculated K =
from equilbrium concentrations
Sinex 2008
5 3 2
3 2
5
5 o
PCl PCl + Cl
(PCl )(Cl )K =
(PCl )
(x)(x)K =(PCl ) -x
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To use Solver: The Solver must be loaded as an add-in in Excel to function!!!
Click on Solver
Solver Parameters are pre-set
except for the value of K.
Excel 2007 - Solver is on the Data tab.
Sinex 2008
left-side
guess cell
right-side
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How to set this up to solve the equation
1. The blue arrowsshow which cells or values feed into the right-side formula:
The left-side is The right-side is the
the value of K expression equal to K
and is just reading
that value in here.
2. Here are the cell references that go into the Solver Parameters:
Solver is going to vary the value of the guess cell (x),
which feeds into the right-side equation, until it gets
the right-side to equal the left-side.
Sinex 2008
select value of
K or left-side
place the guess cell here
right-side
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