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10HSCN + 8e− → (NH4)2S + 8SCN− + H2S↑ + 2C

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Reduction of thiocyanic acid
10HSCNThiocyanic acid + 8e−Electron
⟶
(NH4)2SAmmonium sulfide + 8SCN−Thiocyanate ion + H2S↑Hydrogen sulfide + 2CCarbon

Reduction of thiocyanic acid yields ammonium sulfide, thiocyanate ion, hydrogen sulfide, and carbon (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 thiocyanic acid
10HSCNThiocyanic acid + 8e−Electron
⟶
(NH4)2SAmmonium sulfide + 8SCN−Thiocyanate ion + H2S↑Hydrogen sulfide + 2CCarbon

General equation

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

Oxidation state of each atom

Reduction of thiocyanic acid

Reactants

Chemical formulaNameCoefficientTypeType in general
equation
HSCNThiocyanic acid10
Oxidizing
–
e−Electron8
–
Electron

Products

Chemical formulaNameCoefficientTypeType in general
equation
(NH4)2SAmmonium sulfide1
–
–
SCN−Thiocyanate ion8
–
–
H2SHydrogen sulfide1
–
–
CCarbon2
Reduced
–

Thermodynamic changes

Changes in aqueous solution (1)

Reduction of thiocyanic acid
◆
ΔrG−291.6 kJ/mol
K1.22 × 1051
pK−51.09
10HSCNIonized aqueous solution + 8e−
⟶
(NH4)2SIonized aqueous solution + 8SCN−Un-ionized aqueous solution + H2S↑Gas + 2CCrystalline solidgraphite
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
−405.3−291.6140.8–
per 1 mol of
−40.53−29.1614.08–
per 1 mol of
Electron
−50.66−36.4517.60–
per 1 mol of
−405.3−291.6140.8–
per 1 mol of
Thiocyanate ion
−50.66−36.4517.60–
per 1 mol of
−405.3−291.6140.8–
per 1 mol of
−202.7−145.870.40–

Changes in aqueous solution (2)

Reduction of thiocyanic acid
◆
ΔrG−285.9 kJ/mol
K1.22 × 1050
pK−50.09
10HSCNIonized aqueous solution + 8e−
⟶
(NH4)2SIonized aqueous solution + 8SCN−Un-ionized aqueous solution + H2S↑Un-ionized aqueous solution + 2CCrystalline solidgraphite
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
−424.4−285.956–
per 1 mol of
−42.44−28.595.6–
per 1 mol of
Electron
−53.05−35.747.0–
per 1 mol of
−424.4−285.956–
per 1 mol of
Thiocyanate ion
−53.05−35.747.0–
per 1 mol of
−424.4−285.956–
per 1 mol of
−212.2−142.928–

Changes in aqueous solution (3)

Reduction of thiocyanic acid
◆
ΔrG−340.1 kJ/mol
K3.83 × 1059
pK−59.58
10HSCNUn-ionized aqueous solution + 8e−
⟶
(NH4)2SIonized aqueous solution + 8SCN−Un-ionized aqueous solution + H2S↑Gas + 2CCrystalline solidgraphite
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
–−340.1––
per 1 mol of
–−34.01––
per 1 mol of
Electron
–−42.51––
per 1 mol of
–−340.1––
per 1 mol of
Thiocyanate ion
–−42.51––
per 1 mol of
–−340.1––
per 1 mol of
–−170.1––

Changes in aqueous solution (4)

Reduction of thiocyanic acid
◆
ΔrG−334.4 kJ/mol
K3.84 × 1058
pK−58.58
10HSCNUn-ionized aqueous solution + 8e−
⟶
(NH4)2SIonized aqueous solution + 8SCN−Un-ionized aqueous solution + H2S↑Un-ionized aqueous solution + 2CCrystalline solidgraphite
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
–−334.4––
per 1 mol of
–−33.44––
per 1 mol of
Electron
–−41.80––
per 1 mol of
–−334.4––
per 1 mol of
Thiocyanate ion
–−41.80––
per 1 mol of
–−334.4––
per 1 mol of
–−167.2––

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
HSCN (ai)76.44[1]92.71[1]144.3[1]-40.2[1]
HSCN (ao)–97.56[1]––
e−––––
* (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
(NH4)2S (ai)-231.8[1]-72.6[1]212.1[1]–
SCN− (ao)76.44[1]92.71[1]144.3[1]-40.2[1]
H2S (g)-20.63[1]-33.56[1]205.79[1]34.23[1]
H2S (ao)-39.7[1]-27.83[1]121[1]–
C (cr)
graphite
0[1]0[1]5.740[1]8.527[1]
C (cr)
diamond
1.895[1]2.900[1]2.377[1]6.113[1]
C (g)716.682[1]671.257[1]158.096[1]20.838[1]
* (ai):Ionized aqueous solution, (ao):Un-ionized aqueous solution, (g):Gas, (cr):Crystalline solid

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)