Chemistry

13 s and p – Block ElementsThe aluminium chloride reacts with the water rather than just dissolving in it. In the firstinstance, hexaaquaaluminium ions are formed together with chloride ions.3AlCl 6H O 3(s) 2 (l) AlH O2 3Cl6 (aq)(aq)You will see that this is very similar to the magnesium chloride equation given above - theonly real difference is the charge on the ion.Summary At room temperature, solid aluminium chloride has an ionic lattice with a lot of covalentcharacter. At temperatures around 180 - 190°C (depending on the pressure), aluminium chlorideconverts to a molecular form, Al2Cl6. This causes it to melt or vaporise because there arenow only comparatively weak intermolecular attractions. As the temperature increases a bit more, it increasingly breaks up into simple AlCl3molecules.Silicon Tetrachloride, SiCl4Silicon tetrachloride is a simple covalent chloride. There isn't enough electronegativitydifference between the silicon and the chlorine for the two to form ionic bonds.It fumes in moist air because it reacts with waterin the air to produce hydrogen chloride. If you addwater to silicon tetrachloride, there is a violent reactionto produce silicon dioxide and fumes of hydrogenchloride. In a large excess of water, the hydrogenchloride will, of course, dissolve to give a stronglyacidic solution containing hydrochloric acid.Do you know?Silicon tetrachloride is a colourless liquidat room temperature, which fumes inmoist air. The only attractions betweenthe molecules are van der Waalsdispersion forces.It does not conduct electricity becauseof the lack of ions or mobile electrons.23The Phosphorus ChloridesThere are two phosphorus chlorides - phosphorus(III) chloride, (PCl3), and phosphorus(V)chloride, (PCl5).Phosphorus (III) Chloride (phosphorus Trichloride),(PCl ).3This is another simple covalent chloride - again afuming liquid at room temperature.Phosphorus(III) chloride reacts violently with water.You get phosphorous acid, H3PO3, and fumes ofhydrogen chloride (or a solution containing hydrochloricacid if lots of water is used).Do you know?Phosphorus trichloride is a liquidbecause there are only van derWaals dispersion forces and dipoledipoleattractions between themolecules. It does not conductelectricity because of the lack of ionsor mobile electrons.Phosphorus (V) Chloride (Phosphorus pentachloride), ((PCl ).5Unfortunately, phosphorus (V) chloride is structurally more complicated.