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Properties of substance:

phosphoric acid

Synonyms:

orthophosphoric acid

Group of substances:

inorganic

Physical appearance:

colorless monoclinic crystals

Empirical formula (Hill's system for organic substances):

H3O4P

Structural formula as text:

H3PO4

Molar/atomic mass: 97.995

Melting point (°C):

42.35

Decomposition temperature (°C):

213

Solubility (g/100 g of solvent):

diethyl ether: 525 (20°C) [Ref.]
ethanol: soluble [Ref.]
water: 329.2 (-16.3°C) [Ref.]
water: 369.5 (0.5°C) [Ref.]
water: 548 (20°C) [Ref.]
water: 599.3 (24.03°C) [Ref.]
water: miscible (42.3°C) [Ref.]

Properties of solutions:

10% (wt.), solvent - water
  Viscosity (mPa·s) = 1.1 (25°)
  Density (g/cm3) = 1.05223 (25°)
  Freezing point (°C) = -2.1
  Boiling point (°C) = 100.2
20% (wt.), solvent - water
  Density (g/cm3) = 1.1129 (25°)
30% (wt.), solvent - water
  Density (g/cm3) = 1.1794 (25°)
40% (wt.), solvent - water
  Dynamic viscosity (mPa·s) = 3.856 (20°)
  Density (g/cm3) = 1.2536 (20°)
  Density (g/cm3) = 1.2527 (25°)
  Index of refraction = 1.3735 (20°)
  Freezing point (°C) = -23.58
50% (wt.), solvent - water
  Density (g/cm3) = 1.3334 (25°)
  Freezing point (°C) = -41.9
  Boiling point (°C) = 104.
60% (wt.), solvent - water
  Viscosity (mPa·s) = 9.2 (25°)
  Density (g/cm3) = 1.4223 (25°)
  Freezing point (°C) = -76.9
  Boiling point (°C) = 114.9
62,5% (wt.), solvent - water
  Freezing point (°C) = -85.
70% (wt.), solvent - water
  Viscosity (mPa·s) = 15.4 (25°)
  Density (g/cm3) = 1.52 (25°)
  Freezing point (°C) = -43.
80% (wt.), solvent - water
  Density (g/cm3) = 1.6275 (25°)
  Freezing point (°C) = -4.6
90% (wt.), solvent - water
  Freezing point (°C) = 28.8

Hygroscopic:

very hygroscopic

Interatomic distances and bond angles:

Interatomic distances (in pm): 157 (P-OH)
Interatomic distances (in pm): 152 (P=O)

Numerical data:

Year of discovery: 1671
Electrical Conductivity (mS/cm): 46.8

Density:

1.87 (20°C, g/cm3)

Reactions of synthesis:

  1. [Ref.1, Ref.2aster, Ref.3aster]
    2P + 4HNO3 + H2O → 2H3PO4 + 3NO + NO2
  2. [Ref.1aster, Ref.2aster]
    Na2HPO4 + 2HCl → H3PO4 + 2NaCl
  3. [Ref.1aster]
    P2O5 + 3H2O → 2H3PO4

Reactions:

  1. [Ref.1aster]
    KOH + HBF4 → KBF4 + H2O
  2. [Ref.1]
    KI + H3PO4 → HI + KH2PO4

Dissociation:

H0 (1) = -5.2 (25°C)
pKBH+ (1) = -3 (25°C, water)
pKa (1) = 2.12 (25°C, water)
pKa (1) = 4.4 (25°C, acetic acid)
pKa (2) = 7.2 (25°C, water)
pKa (3) = 11.9 (25°C, water)

Permittivity (dielectric constant):

61 (25°C)

Viscosity (mPa·s):

76.5 (45°C)
177.7 (25°C)

Standard molar enthalpy (heat) of formation ΔfH0 (298.15 K, kJ/mol):

-1279 (s)

Standard molar Gibbs energy of formation ΔfG0 (298.15 K, kJ/mol):

-1119.1 (s)

Standard molar entropy S0 (298.15 K, J/(mol·K)):

110.5 (s)

Molar heat capacity at constant pressure Cp (298.15 K, J/(mol·K)):

106.1 (s)

Molar enthalpy (heat) of fusion ΔfusH (kJ/mol):

13

Standard molar enthalpy (heat) of formation ΔfH0 (298.15 K, kJ/mol):

-1271.7 (l)

Standard molar Gibbs energy of formation ΔfG0 (298.15 K, kJ/mol):

-1123.6 (l)

Standard molar entropy S0 (298.15 K, J/(mol·K)):

150.8 (l)

Molar heat capacity at constant pressure Cp (298.15 K, J/(mol·K)):

145 (l)

LD50 (mg/kg):

1250 (rats, oral)
1250 (mice, oral)

References:

  1. CRC Handbook of Chemistry and Physics. - 90ed. - CRC Press, 2010. - pp. 5-13
  2. Comey A. M., Hahn D. A. A dictionary of Chemical Solubilities Inorganic. - 2 ed. - New York, The MacMillan Company, 1921. - pp. 672-674
  3. Holleman A.F., Wiberg E., Wiberg N. Lehrbuch der Anorganischen Chemie. - Berlin: Walter de Gruyter, 1995. - pp. 238
  4. Inorganic Syntheses. - Vol. 1. - New York and London, 1939. - pp. 101-103
  5. Seidell A. Solubilities of inorganic and metal organic compounds. - 3ed., vol.1. - New York: D. Van Nostrand Company, 1940. - pp. 592-594
  6. Seidell A. Solubilities of inorganic and metal organic compounds. - 3ed., vol.1. - New York: D. Van Nostrand Company, 1940. - pp. 592-594
  7. Вредные вещества в промышленности: Справочник для химиков, инженеров и врачей. - 7-е изд., Т.3. - Л.: Химия, 1976. - pp. 132-133 [Russian]
  8. Вредные химические вещества: Неорганические соединения элементов V-VIII групп. Справочник. - Л., 1989. - pp. 73 [Russian]
  9. Лурье Ю.Ю. Справочник по аналитической химии. - М.: Химия, 1979. - pp. 91 [Russian]
  10. Некрасов Б.В. Основы общей химии. - Т.1. - М.: Химия, 1973. - pp. 449 [Russian]
  11. Постников Н.Н. Термическая фосфорная кислота. Химия и технология. - М.: Химия, 1970 [Russian]
  12. Рабинович В.А., Хавин З.Я. Краткий химический справочник. - Л.: Химия, 1977. - pp. 109, 219 [Russian]
  13. Справочник по растворимости. - Т.1, Кн.1. - М.-Л.: ИАН СССР, 1961. - pp. 332, 926 [Russian]
  14. Справочник химика. - Т. 3. - М.-Л.: Химия, 1965. - pp. 118 [Russian]
  15. Химическая энциклопедия. - Т. 5. - М.: Советская энциклопедия, 1999. - pp. 153-156 [Russian]

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    © Collected Ruslan Anatolievich Kiper, burewestnik@mail.ru