Hydroiodic acid (data page)

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This page provides additional chemical data on hydroiodic acid.

Contents

[edit] Material Safety Data Sheet

The handling of this chemical may incur notable safety precautions. It is highly recommend that you seek the Material Safety Datasheet (MSDS) for this chemical from a reliable source such as SIRI, and follow its directions.

[edit] Structure and properties

Structure and properties
Index of refraction, nD  ?
Abbe number ?
Dielectric constant, εr  ? ε0 at ? °C
Bond strength  ?
Bond length  ?
Bond angle  ?
Magnetic susceptibility  ?


[edit] Hydroiodic acid

Once again, although chemically related, hydroiodic acid is not HI but made from it. Commercial "concentrated" hydroiodic acid usually contains 48% - 57% HI by weight. The solution forms an azeotrope boiling at 127 °C at 57% HI, 43% water. Hydroiodidic acid is one of the strongest of all the common halide acids, despite the fact that the electronegativity of iodine is weaker than the rest of the other common halides. The high acidity is caused by the dispersal of the ionic charge over the anion. The iodide ion is much larger than the other common halides which results in the negative charge being dispersed over a large space. By contrast, a chloride ion is much smaller, meaning its negative charge is more concentrated, leading to a stronger interaction between the proton and the chloride ion. This weaker H+---I− interaction in HI facilitates dissociation of the proton from the anion .

HI(g) + H2O(l) ⇌ H3O+(aq) + I–(aq)        (Ka ≈ 1010)
HBr(g) + H2O(l) ⇌ H3O+(aq) + Br–(aq)        (Ka ≈ 109)
HCl(g) + H2O(l) ⇌ H3O+(aq) + Cl–(aq)        (Ka ≈ 108)

[edit] Thermodynamic properties

Phase behavior
Triple point  ? K (? °C), ? Pa
Critical point  ? K (? °C), ? Pa
Std enthalpy change
of fusion, ΔfusHo		  ? kJ/mol
Std entropy change
of fusion, ΔfusSo		  ? J/(mol·K)
Std enthalpy change
of vaporization, ΔvapHo		  ? kJ/mol
Std entropy change
of vaporization, ΔvapSo		  ? J/(mol·K)
Solid properties
Std enthalpy change
of formation, ΔfHosolid		  ? kJ/mol
Standard molar entropy,
Sosolid		  ? J/(mol K)
Heat capacity, cp  ? J/(mol K)
Liquid properties
Std enthalpy change
of formation, ΔfHoliquid		  ? kJ/mol
Standard molar entropy,
Soliquid		  ? J/(mol K)
Heat capacity, cp  ? J/(mol K)
Gas properties
Std enthalpy change
of formation, ΔfHogas		  ? kJ/mol
Standard molar entropy,
Sogas		  ? J/(mol K)
Heat capacity, cp  ? J/(mol K)

[edit] Spectral data

UV-Vis
λmax  ? nm
Extinction coefficient, ε  ?
IR
Major absorption bands  ? cm−1
NMR
Proton NMR  
Carbon-13 NMR  
Other NMR data  
MS
Masses of
main fragments		  

[edit] References

Except where noted otherwise, data relate to standard ambient temperature and pressure.

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