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10H3PO4 + 5e− → P + 9H2PO4− + 4H3O+

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Reduction of phosphoric acid
10H3PO4Phosphoric acid + 5e−Electron
⟶
PPhosphorus + 9H2PO4−Dihydrogenphosphate ion + 4H3O+Hydronium ion

Reduction of phosphoric acid yields phosphorus, dihydrogenphosphate ion, and hydronium ion (Other reactions are here). This reaction is an oxidation-reduction reaction and is classified as follows:

Table of contents
  1. 1Reaction data
  2. 2Thermodynamic changes
  3. 3References
  4. 4Related reactions
  5. 5Related categories

Reaction data

Chemical equation

Reduction of phosphoric acid
10H3PO4Phosphoric acid + 5e−Electron
⟶
PPhosphorus + 9H2PO4−Dihydrogenphosphate ion + 4H3O+Hydronium ion

General equation

Reduction of reducible species
ReactantOxidizing agent + e−
⟶
ProductReduction product

Oxidation state of each atom

Reduction of phosphoric acid

Reactants

Chemical formulaNameCoefficientTypeType in general
equation
H3PO4Phosphoric acid10
Oxidizing
–
e−Electron5
–
Electron

Products

Chemical formulaNameCoefficientTypeType in general
equation
PPhosphorus1
Reduced
–
H2PO4−Dihydrogenphosphate ion9
–
–
H3O+Hydronium ion4
–
–

Thermodynamic changes

Changes in standard condition (1)

Reduction of phosphoric acid
◆
ΔrG304.36 kJ/mol
K0.48 × 10−53
pK53.32
10H3PO4Un-ionized aqueous solution + 5e−
⟶
PCrystalline solidwhite + 9H2PO4−Un-ionized aqueous solution + 4H3O+Un-ionized aqueous solution
Standard enthalpy
of reaction
ΔrH°
kJ · mol−1		Standard
Gibbs energy
of reaction
ΔrG°
kJ · mol−1		Standard entropy
of reaction
ΔrS°
J · K−1 · mol−1		Standard heat
capacity of reaction
at constant pressure
ΔrCp°
J · K−1 · mol−1
per 1 mol of
Equation
73.47304.36−447.7–
per 1 mol of
7.34730.436−44.77–
per 1 mol of
Electron
14.6960.872−89.54–
per 1 mol of
73.47304.36−447.7–
per 1 mol of
Dihydrogenphosphate ion
8.16333.818−49.74–
per 1 mol of
Hydronium ion
18.3776.090−111.9–

Changes in standard condition (2)

Reduction of phosphoric acid
◆
ΔrG−934.0 kJ/mol
K4.26 × 10163
pK−163.63
10H3PO4Ionized aqueous solution + 5e−
⟶
PCrystalline solidwhite + 9H2PO4−Un-ionized aqueous solution + 4H3O+Un-ionized aqueous solution
Standard enthalpy
of reaction
ΔrH°
kJ · mol−1		Standard
Gibbs energy
of reaction
ΔrG°
kJ · mol−1		Standard entropy
of reaction
ΔrS°
J · K−1 · mol−1		Standard heat
capacity of reaction
at constant pressure
ΔrCp°
J · K−1 · mol−1
per 1 mol of
Equation
−35.9−934.03337.3–
per 1 mol of
−3.59−93.40333.73–
per 1 mol of
Electron
−7.18−186.8667.46–
per 1 mol of
−35.9−934.03337.3–
per 1 mol of
Dihydrogenphosphate ion
−3.99−103.8370.81–
per 1 mol of
Hydronium ion
−8.97−233.5834.33–

Changes in standard condition (3)

Reduction of phosphoric acid
◆
ΔrG304.36 kJ/mol
K0.48 × 10−53
pK53.32
10H3PO4Un-ionized aqueous solution + 5e−
⟶
PCrystalline solidwhite + 9H2PO4−Un-ionized aqueous solution + 4H3O+Un-ionized aqueous solution
Standard enthalpy
of reaction
ΔrH°
kJ · mol−1		Standard
Gibbs energy
of reaction
ΔrG°
kJ · mol−1		Standard entropy
of reaction
ΔrS°
J · K−1 · mol−1		Standard heat
capacity of reaction
at constant pressure
ΔrCp°
J · K−1 · mol−1
per 1 mol of
Equation
73.47304.36−447.7–
per 1 mol of
7.34730.436−44.77–
per 1 mol of
Electron
14.6960.872−89.54–
per 1 mol of
73.47304.36−447.7–
per 1 mol of
Dihydrogenphosphate ion
8.16333.818−49.74–
per 1 mol of
Hydronium ion
18.3776.090−111.9–

Thermodynamic data of reactants

Chemical formulaStandard enthalpy
of formation
ΔfH°
kJ · mol−1		Standard Gibbs
energy of
formation
ΔfG°
kJ · mol−1		Standard
molar entropy
S°
J · K−1 · mol−1		Standard molar
heat capacity at
constant pressure
Cp°
J · K−1 · mol−1
H3PO4 (cr)-1279.0[1]-1119.1[1]110.50[1]106.06[1]
H3PO4 (l)-1266.9[1]–––
H3PO4 (ai)-1277.4[1]-1018.7[1]-220.3[1]–
H3PO4 (ao)-1288.34[1]-1142.54[1]158.2[1]–
H3PO4 (cr)
0.5 hydrate
-1431.3[1]-1242.1[1]129.16[1]126.02[1]
H3PO4 (cr)
1 hydrate
-1568.83[1]–––
e−––––
* (cr):Crystalline solid, (l):Liquid, (ai):Ionized aqueous solution, (ao):Un-ionized aqueous solution

Thermodynamic data of products

Chemical formulaStandard enthalpy
of formation
ΔfH°
kJ · mol−1		Standard Gibbs
energy of
formation
ΔfG°
kJ · mol−1		Standard
molar entropy
S°
J · K−1 · mol−1		Standard molar
heat capacity at
constant pressure
Cp°
J · K−1 · mol−1
P (cr)
white
0[1]0[1]41.09[1]23.84[1]
P (cr)
red, triclinic
-17.6[1]-12.1[1]22.80[1]21.21[1]
P (cr)
black
-39.3[1]–––
P (am)
red
-7.5[1]–––
P (g)314.64[1]278.25[1]163.193[1]20.786[1]
H2PO4− (ao)-1296.29[1]-1130.28[1]90.4[1]–
H3O+ (ao)-285.830[1]-237.129[1]69.91[1]75.291[1]
* (cr):Crystalline solid, (am):Amorphous solid, (g):Gas, (ao):Un-ionized aqueous solution

References

List of references

  1. 1
    Janiel J. Reed (1989)
    The NBS Tables of Chemical Thermodynamic Properties: Selected Values for Inorganic and C1 and C2 Organic Substances in SI Units
    National Institute of Standards and Technology (NIST)