Group 17 Elements | Oxoacids and Interhalogen Compounds#
Oxoacids of Halogens#
- An oxoacid can be defined as an acid that contains oxygen and atleast one other element and atleast one hydrogen atom bonded to oxygen.
| Acid | Fluorine | Chlorine | Bromine | Iodine |
|---|---|---|---|---|
| Halic(I) acid (Hypohalous acid) | HOF (Hypofluorous acid) | HOCl (Hypochlorous acid) | HOBr (Hypobromous acid) | HOI (Hypoiodous acid) |
| Halic(III) acid (Halous acid) | - | HOClO (Chlorous acid) | - | - |
| Halic(V) acid (Halic acid) | - | HOClO2 (Chloric acid) | HOBrO2 (Bromic acid) | HOIO2 (Iodic acid) |
| Halic(VII) acid (Perhalic acid) | - | HOClO3 (Perchloric acid) | HOBrO3 (Perbromic acid) | HOIO3 (Periodic acid) |
Structures of oxoacids#
Structures of oxoacids
1. Hypochlorous acid (HOCl)#
2. Chlorous acid (HOClO)#
3. Chloric acid (HOClO2)#
4. Perchloric acid (HOClO3)#
Interhalogen Compounds#
Halogens combine amongst themselves to form a number of compounds known as interhalogens of the type XX', XX'3, XX'5, XX'7, where X is a large size halogen and X' is a small size halogen.
1. Preparation of interhalogen compounds#
- Interhalogen compounds are prepared by direct combination of halogens under specific conditions.
\[At\ 437\ K:\ Cl_2 + F_2 → 2ClF\]
\[[Cl_2\ and\ F_2\ are\ in\ equal\ volume]\]
\[At\ 573\ K:\ Cl_2 + 3F_2 → 2ClF_3\]
\[[F_2\ is\ in\ excess]\]
\[I_2 + Cl_2 → 2ICl\]
\[[I_2\ and\ Cl_2\ are\ equimolar]\]
\[I_2 + 3Cl_2 → 2ICl_3\]
\[[Cl_2\ is\ in\ excess]\]
\[Br_2 + 3F_2 → 2BrF_3\]
\[[F_2\ is\ diluted\ with\ water]\]
\[Br_2 + 5F_2 → 2BrF_5\]
\[[F_2\ is\ in\ excess]\]
2. Properties of Interhalogen compounds#
- Interhalogen compounds are all covalent molecules and are diamagnetic in nature.
- These are volatile solids or liquids at 298 K except ClF which is a gas.
- Interhalogen compounds are more reactive than halogens (except fluorine) because X-X' bond in interhalogens is weaker than X-X bond in halogens ecxcept F-F bond.
| Type | Formula | Physical state and colour | Structure |
|---|---|---|---|
| XX' | ClF | Colourless Gas | - |
| XX' | BrF | Pale brown gas | - |
| XX' | IF | Detected spectroscopically | - |
| XX' | BrCl | Gas | - |
| XX' | ICl | Solid | - |
| XX'3 | ClF3 | Colourless Gas | Bent T-shaped |
| XX'3 | BrF3 | Yellow green | Bent T-shaped |
| XX'3 | IF3 | Yellow Powder | Bent T-shaped |
| XX'3 | ICl3 | Orange solid | Bent T-shaped |
| XX'5 | IF5 | Colourless gas but solid below 77 K | Square Pyramidal |
| XX'5 | BrF5 | Colourless liquid | Square Pyramidal |
| XX'5 | ClF5 | Colourless liquid | Square Pyramidal |
| XX'7 | IF7 | Colourless gas | Pentagonal bipyramidal |
Uses of interhalogen compounds#
- Interhalogen compounds are used as fluorinating agents. For example, ClF3 and BrF3 are used to prepare UF6.
\[U_{(s)} + 3ClF_{3(l)} → UF_{6(g)} + 3ClF_{(g)}\]
- Interhalogen compounds are used as non-aqueous solvents.
Question#
Discuss the molecular shape of BrF3 on the basis of VSEPR theory.
The structure of BrF3 is:
Geometry: Trigonal bipyrmaidal, Shape: Bent T-shaped, Hybridization: sp3d