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Properties of substance:

diphosphoric acid

Group of substances:

inorganic

Physical appearance:

colorless crystals

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

H4O7P2

Structural formula as text:

H4P2O7

Molar/atomic mass: 177.97

Melting point (°C):

61

Decomposition temperature (°C):

300

Solubility (g/100 g of solvent):

diethyl ether: very soluble [Ref.]
ethanol: very soluble [Ref.]
water: 709 (23°C) [Ref.]
water: reaction (100°C) [Ref.]

Dissociation:

pKa (1) = 0.85 (18°C, water)
pKa (2) = 1.95 (25°C, water)
pKa (3) = 6.68 (25°C, water)
pKa (4) = 9.39 (25°C, water)

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

-2242 (s)

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

9.2

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

-2231.7 (l)

LD50 (mg/kg):

1170 (mice, )

References:

  1. CRC Handbook of Chemistry and Physics. - 90ed. - CRC Press, 2010. - pp. 5-14
  2. Некрасов Б.В. Основы общей химии. - Т.1. - М.: Химия, 1973. - pp. 450 [Russian]
  3. Рабинович В.А., Хавин З.Я. Краткий химический справочник. - Л.: Химия, 1977. - pp. 109 [Russian]
  4. Справочник по растворимости. - Т.1, Кн.1. - М.-Л.: ИАН СССР, 1961. - pp. 333 [Russian]

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    © Collected Ruslan Anatolievich Kiper, burewestnik@mail.ru