Home
Chemical reactions
2NaCN + H2SeO3 → Na2SeO3 + 2HCN

2NaCN + H₂SeO₃ → Na₂SeO₃ + 2HCN

Last updated: June 13, 2022

Reaction of sodium cyanide and selenous acid: 2NaCNSodium cyanide + H₂SeO₃Selenous acid
⟶
Na₂SeO₃Sodium selenite + 2HCNHydrogen cyanide

The reaction of sodium cyanide and selenous acid yields sodium selenite and hydrogen cyanide. This reaction is an acid-base reaction and is classified as follows:

Reaction of salt of volatile acid and nonvolatile acid with generating volatile acid

Table of contents

Reaction data

Reactants

Chemical formula	Name	Coefficient	Type	Type in general equation
NaCN	Sodium cyanide	2	Brønsted base	Salt of volatile acid
H₂SeO₃	Selenous acid	1	Brønsted acid	Nonvolatile acid

Products

Chemical formula	Name	Coefficient	Type	Type in general equation
Na₂SeO₃	Sodium selenite	1	Conjugate base	Salt of non volatile acid
HCN	Hydrogen cyanide	2	Conjugate acid	Volatile acid

Thermodynamic changes

Changes in standard condition (1)

Reaction of sodium cyanide and selenous acid: 2NaCNCrystalline solidcubic + H₂SeO₃Crystalline solid
⟶
Na₂SeO₃Crystalline solid + 2HCNLiquid

	Standard enthalpy of reaction Δ_rH° kJ · mol⁻¹	Standard Gibbs energy of reaction Δ_rG° kJ · mol⁻¹	Standard entropy of reaction Δ_rS° J · K⁻¹ · mol⁻¹	Standard heat capacity of reaction at constant pressure Δ_rC_p° J · K⁻¹ · mol⁻¹
per 1 mol of Equation	−41.4	–	–	–
per 1 mol of Sodium cyanide	−20.7	–	–	–
per 1 mol of Selenous acid	−41.4	–	–	–
per 1 mol of Sodium selenite	−41.4	–	–	–
per 1 mol of Hydrogen cyanide	−20.7	–	–	–

Changes in standard condition (2)

Reaction of sodium cyanide and selenous acid: 2NaCNCrystalline solidorthorhombic + H₂SeO₃Crystalline solid
⟶
Na₂SeO₃Crystalline solid + 2HCNLiquid

	Standard enthalpy of reaction Δ_rH° kJ · mol⁻¹	Standard Gibbs energy of reaction Δ_rG° kJ · mol⁻¹	Standard entropy of reaction Δ_rS° J · K⁻¹ · mol⁻¹	Standard heat capacity of reaction at constant pressure Δ_rC_p° J · K⁻¹ · mol⁻¹
per 1 mol of Equation	−34.9	–	–	–
per 1 mol of Sodium cyanide	−17.4	–	–	–
per 1 mol of Selenous acid	−34.9	–	–	–
per 1 mol of Sodium selenite	−34.9	–	–	–
per 1 mol of Hydrogen cyanide	−17.4	–	–	–

Changes in aqueous solution (1)

Reaction of sodium cyanide and selenous acid ◆ Δ_rG −49.2 kJ/mol K 4.16 × 10⁸ pK −8.62: 2NaCNIonized aqueous solution + H₂SeO₃Un-ionized aqueous solution
⟶
Na₂SeO₃Ionized aqueous solution + 2HCNUn-ionized aqueous solution

	Standard enthalpy of reaction Δ_rH° kJ · mol⁻¹	Standard Gibbs energy of reaction Δ_rG° kJ · mol⁻¹	Standard entropy of reaction Δ_rS° J · K⁻¹ · mol⁻¹	Standard heat capacity of reaction at constant pressure Δ_rC_p° J · K⁻¹ · mol⁻¹
per 1 mol of Equation	−88.8	−49.2	−135	–
per 1 mol of Sodium cyanide	−44.4	−24.6	−67.5	–
per 1 mol of Selenous acid	−88.8	−49.2	−135	–
per 1 mol of Sodium selenite	−88.8	−49.2	−135	–
per 1 mol of Hydrogen cyanide	−44.4	−24.6	−67.5	–

Changes in aqueous solution (2)

Reaction of sodium cyanide and selenous acid: 2NaCNIonized aqueous solution + H₂SeO₃Aqueous solution
⟶
Na₂SeO₃Ionized aqueous solution + 2HCNUn-ionized aqueous solution

	Standard enthalpy of reaction Δ_rH° kJ · mol⁻¹	Standard Gibbs energy of reaction Δ_rG° kJ · mol⁻¹	Standard entropy of reaction Δ_rS° J · K⁻¹ · mol⁻¹	Standard heat capacity of reaction at constant pressure Δ_rC_p° J · K⁻¹ · mol⁻¹
per 1 mol of Equation	−89.0	–	–	–
per 1 mol of Sodium cyanide	−44.5	–	–	–
per 1 mol of Selenous acid	−89.0	–	–	–
per 1 mol of Sodium selenite	−89.0	–	–	–
per 1 mol of Hydrogen cyanide	−44.5	–	–	–

Changes in aqueous solution (3)

Reaction of sodium cyanide and selenous acid ◆ Δ_rG 56.2 kJ/mol K 0.14 × 10⁻⁹ pK 9.85: 2NaCNIonized aqueous solution + H₂SeO₃Un-ionized aqueous solution
⟶
Na₂SeO₃Ionized aqueous solution + 2HCNIonized aqueous solution

	Standard enthalpy of reaction Δ_rH° kJ · mol⁻¹	Standard Gibbs energy of reaction Δ_rG° kJ · mol⁻¹	Standard entropy of reaction Δ_rS° J · K⁻¹ · mol⁻¹	Standard heat capacity of reaction at constant pressure Δ_rC_p° J · K⁻¹ · mol⁻¹
per 1 mol of Equation	−1.8	56.2	−196	–
per 1 mol of Sodium cyanide	−0.90	28.1	−98.0	–
per 1 mol of Selenous acid	−1.8	56.2	−196	–
per 1 mol of Sodium selenite	−1.8	56.2	−196	–
per 1 mol of Hydrogen cyanide	−0.90	28.1	−98.0	–

Changes in aqueous solution (4)

Reaction of sodium cyanide and selenous acid: 2NaCNIonized aqueous solution + H₂SeO₃Aqueous solution
⟶
Na₂SeO₃Ionized aqueous solution + 2HCNIonized aqueous solution

	Standard enthalpy of reaction Δ_rH° kJ · mol⁻¹	Standard Gibbs energy of reaction Δ_rG° kJ · mol⁻¹	Standard entropy of reaction Δ_rS° J · K⁻¹ · mol⁻¹	Standard heat capacity of reaction at constant pressure Δ_rC_p° J · K⁻¹ · mol⁻¹
per 1 mol of Equation	−2.0	–	–	–
per 1 mol of Sodium cyanide	−1.0	–	–	–
per 1 mol of Selenous acid	−2.0	–	–	–
per 1 mol of Sodium selenite	−2.0	–	–	–
per 1 mol of Hydrogen cyanide	−1.0	–	–	–

Thermodynamic data of reactants

Chemical formula	Standard enthalpy of formation Δ_fH° kJ · mol⁻¹	Standard Gibbs energy of formation Δ_fG° kJ · mol⁻¹	Standard molar entropy S° J · K⁻¹ · mol⁻¹	Standard molar heat capacity at constant pressure C_p° J · K⁻¹ · mol⁻¹
NaCN (cr) cubic	-87.49^[1]	-76.43^[1]	115.60^[1]	70.37^[1]
NaCN (cr) orthorhombic	-90.75^[1]	–	–	–
NaCN (g)	109^[1]	79.94^[1]	249.43^[1]	51.17^[1]
NaCN (ai)	-89.5^[1]	-89.5^[1]	153.1^[1]	–
NaCN (cr) 1/2 hydrate	-235.77^[1]	–	–	–
NaCN (cr) 2 hydrate	-679.77^[1]	–	–	–
H₂SeO₃ (cr)	-524.46^[1]	–	–	–
H₂SeO₃ (ao)	-507.48^[1]	-426.14^[1]	207.9^[1]	–
H₂SeO₃ (aq)	-507.27^[1]	–	–	–

* (cr):Crystalline solid, (g):Gas, (ai):Ionized aqueous solution, (ao):Un-ionized aqueous solution, (aq):Aqueous solution

Thermodynamic data of products

Chemical formula	Standard enthalpy of formation Δ_fH° kJ · mol⁻¹	Standard Gibbs energy of formation Δ_fG° kJ · mol⁻¹	Standard molar entropy S° J · K⁻¹ · mol⁻¹	Standard molar heat capacity at constant pressure C_p° J · K⁻¹ · mol⁻¹
Na₂SeO₃ (cr)	-958.6^[1]	–	–	–
Na₂SeO₃ (ai)	-989.5^[1]	-893.7^[1]	130^[1]	–
Na₂SeO₃ (cr) 5 hydrate	-2404.13^[1]	–	–	–
HCN (l)	108.87^[1]	124.97^[1]	112.84^[1]	70.63^[1]
HCN (g)	135.1^[1]	124.7^[1]	201.78^[1]	35.86^[1]
HCN (ai)	150.6^[1]	172.4^[1]	94.1^[1]	–
HCN (ao)	107.1^[1]	119.7^[1]	124.7^[1]	–

* (cr):Crystalline solid, (ai):Ionized aqueous solution, (l):Liquid, (g):Gas, (ao):Un-ionized aqueous solution

References

List of references

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
https://doi.org/10.18434/M32124
National Institute of Standards and Technology (NIST)
Citation list

Δ_rG	−49.2 kJ/mol
K	4.16 × 10⁸
pK	−8.62

Δ_rG	56.2 kJ/mol
K	0.14 × 10⁻⁹
pK	9.85

2NaCN + H2SeO3 → Na2SeO3 + 2HCN

Reaction data

Chemical equation

General equation

Oxidation state of each atom