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Properties of substance:

niobium

Group of substances:

inorganic

Physical appearance:

cubic metal

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

Nb

Structural formula as text:

Nb

Molar/atomic mass: 92.91

Melting point (°C):

2470

Boiling point (°C):

4760

Solubility (g/100 g of solvent):

lithium molten: 0.0008 (700°C) [Ref.]
mercury: insoluble [Ref.]
potassium fused: 0.0001 (700°C) [Ref.]
sodium fused: 0.0035 (700°C) [Ref.]
water: insoluble [Ref.]

Numerical data:

Year of discovery: 1801
Superconducting temperature (K): 9.3

Density:

8.57 (20°C, g/cm3)

Reactions:

  1. [Ref.1]
    4Nb + 5O2 → 2Nb2O5

Vapour pressure (Torr):

0.1 (2980°C)
1 (3300°C)
10 (3780°C)
100 (4240°C)

Electrode potential:

Nb3+ + 3e- → Nb, E = -1.1 V (water, 25°C)

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

0 (s)

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

0 (s)

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

36.6 (s)

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

24.6 (s)

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

28

Enthalpy (heat) of vaporization ΔvapH (kJ/mol):

662

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

723 (g)

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

186.2 (g)

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

30.2 (g)

References:

  1. Гибало И.М. Аналитическая химия ниобия и тантала. - М.: Наука, 1967. - pp. 14-15 [Russian]
  2. Гурвич Я.А. Справочник молодого аппаратчика-химика. - М.: Химия, 1991. - pp. 51 [Russian]
  3. Ниобий и тантал. - М.: Металлургия, 1990 [Russian]
  4. Рабинович В.А., Хавин З.Я. Краткий химический справочник. - Л.: Химия, 1977. - pp. 88 [Russian]
  5. Редкие и рассеянные элементы. Химия и технология. - Кн. 2. - М.: Мисис, 1998. - pp. 258-262 [Russian]
  6. Химическая энциклопедия. - Т. 3. - М.: Советская энциклопедия, 1992. - pp. 249-251 [Russian]

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    © Collected Ruslan Anatolievich Kiper, burewestnik@mail.ru