Oxyacids (oxoacids) of p-block elements contain an acidic hydrogen attached to an oxygen atom (-OH) and a central atom bonded to oxygen (E=O). Major examples include phosphorus, sulfur, and chlorine, which form complex series with oxidation states usually ranging from +1 to +5, featuring characteristic tetrahedral geometry.
1. Oxyacids of Nitrogen (Group 15)
| Oxyacid | Formula | Oxidation State of N | Name |
|---|---|---|---|
| Nitrous acid | HNO2 | +3 | Nitrous acid |
| Nitric acid | HNO3 | +5 | Nitric acid |
2. Oxyacids of Phosphorus (Group 15)
| Oxyacid | Formula | Oxidation State of P | Basicity |
|---|---|---|---|
| Hypophosphorous acid | H3PO2 | +1 | Monobasic |
| Phosphorous acid | H3PO3 | +3 | Dibasic |
| Orthophosphoric acid | H3PO4 | +5 | Tribasic |
| Pyrophosphoric acid | H4P2O7 | +5 | Tetrabasic |
3. Oxyacids of Sulfur (Group 16)
| Oxyacid | Formula | Oxidation State of S | Name |
|---|---|---|---|
| Sulphurous acid | H2SO3 | +4 | Sulphurous acid |
| Sulphuric acid | H2SO4 | +6 | Sulphuric acid |
| Thiosulphuric acid | H2S2O3 | +6 & -2 | Thiosulphuric acid |
| Peroxymonosulphuric acid (Caro's acid) | H2SO5 | +6 | Caro's acid |
| Peroxydisulphuric acid (Marshall's acid) | H2S2O8 | +6 | Marshall's acid |
4. Oxyacids of Chlorine (Group 17)
| Oxyacid | Formula | Oxidation State of Cl | Name |
|---|---|---|---|
| Hypochlorous acid | HClO | +1 | Hypochlorous acid |
| Chlorous acid | HClO2 | +3 | Chlorous acid |
| Chloric acid | HClO3 | +5 | Chloric acid |
| Perchloric acid | HClO4 | +7 | Perchloric acid |
Important Note:
• Oxyacids are acids that contain oxygen along with hydrogen and another p-block element.
• Acid strength generally increases with the oxidation state of the central atom and with the number of oxygen atoms.
• For the same oxidation state, acid strength increases from left to right in a period and decreases down a group.
• Oxyacids are acids that contain oxygen along with hydrogen and another p-block element.
• Acid strength generally increases with the oxidation state of the central atom and with the number of oxygen atoms.
• For the same oxidation state, acid strength increases from left to right in a period and decreases down a group.
General Trends in Oxyacids of p-Block Elements
- Oxidation State: Higher oxidation state → stronger acid
- Number of Oxygen Atoms: More oxygen atoms attached to central atom → stronger acid (due to greater dispersal of negative charge on conjugate base)
- Electronegativity of Central Atom: Higher electronegativity → stronger acid
- Stability of Conjugate Base: More stable conjugate base → stronger acid