Hydrogen Halides

Hydrogen Fluoride (HF) m.p. -83.1^oC, b.p. 19.9^oC pKa (aq) 3.17 r(H-F) = 0.92 Å; dipole moment = 1.8D Hydrogen Chloride (HCl) m.p. -114.2^oC, b.p. -85.0 deg.C pKa (aq) -7 r(H-Cl) = 1.28 Å; dipole moment = 1.1D Hydrogen Bromide (HBr) m.p. -86.8^oC, b.p. -66.7^oC pKa (aq) -9 r(H-Br) = 1.41 Å; dipole moment = 0.8D Hydrogen Iodide (HI) m.p. -50.8^oC, b.p. -35.35^oC pKa (aq) -10 r(H-I) = 1.60 Å; dipole moment = 0.4D Synthesis In general HX can be prepared by nonvolatile, nonoxidizing acid on a halide salt. H₂SO₄ good for HF and HCl; H₃PO₄ good for HBr and HI. Anomolous Properties of HF Boiling point. Acid strength in aqueous solution. Strong acid in pure liquid state.