WOLFRAM NOTEBOOK

Stoichiometry

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Before running a reaction the necessary amount of all reactants must be determined. The process of determining those amounts for a given reaction is known as stoichiometry.
Phosphorus pentachloride,
P
Cl
5
, is a common Lewis acid.
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Let’s consider the reaction of 0.275 grams of solid phosphorous,
P
4
, with 500 milliliters of gaseous chlorine,
Cl
2
, to form solid
P
Cl
5
at standard temperature and pressure. What is the limiting reactant and the theoretical yield of
P
Cl
5
?
Start by balancing the chemical reaction:
rxn=ReactionBalance["P4(s)+Cl2(g)->PCl5(s)"]
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ChemicalReaction
P
4
(s)
+
10
Cl
2
(g)
⟶
4P
Cl
5
(s)
Store the stoichiometric coefficients:
react=rxn["ReactantCounts"]​​prod=rxn["ProductCounts"]
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P
4
(s)
1,
Cl
2
(g)
10
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P
Cl
5
(s)
4
Store the amount of
P
4
into a
ChemicalInstance
assuming an uncertainty of ± 0.001 g in the measurement:
p4=ChemicalInstance
P
4
(s)
,Quantity[Around[0.275,0.001],"Grams"]
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ChemicalInstance
P
4
(s)
,
(0.2750
±
0.0010
)
g
Determine the phase and density of
Cl
2
at standard temperature and pressure:
chlorine
CHEMICAL
[{"Phase","Density"}]
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Gas,
0.003214
g/
3
cm
Store the density and amount of
Cl
2
into a
ChemicalInstance
assuming an uncertainty of ± 1 mL in the measurement:
cl2=ChemicalInstance
Cl
2
(g)
,<|"Volume"Quantity[Around[500,1],"Milliters"],"Density"
chlorine
CHEMICAL
["Density"]|>
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ChemicalInstance
Cl
2
(g)
,Volume
(500.0
±
1.0
)
mL
,Density
0.003214
g/
3
cm
Define a function to compute the mole ratio:
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moleRatio[instance_]:=With[​​{moles=instance["Amount"]},​​{instance["Formula"],UnitConvert[moles/react[instance["Chemical"]],"Millimoles"]}​​];
Compute the mole ratios. The smallest ratio indicates the limiting reactant:
Dataset[Map[moleRatio,{p4,cl2}]]
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P
4
(s)
(2.220
±
0.008
)mmol
Cl
2
(g)
(2.267
±
0.005
)mmol
Use the limiting reactant,
P
4
, to compute the theoretical yield of
P
Cl
5
in grams:
ChemicalConvertChemicalInstance
P
Cl
5
(s)
,p4["Amount"]*prod
P
Cl
5
(s)
react
P
4
(s)
,"Grams"
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ChemicalInstance
P
Cl
5
(s)
,
(1.849
±
0.007
)
g
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