ANSWERS: 3
  • This hydrolysis reaction occurs because the atomic radius of the silicon atom is such that the water molecules can attack it, whereas carbon has a smaller atomic radius so the chlorine atoms effectively shield the carbon from attack. Courtesy of the all knowing creature that is Wikipedia.
  • electron configuration of Si is 3s2 3p2, electron config of C is 2s2 2p2. in electron config Si, there are 3d orbital with no electron in it while in C, there is no d orbital. if Si hybrid with Cl to form SiCl4, one electron in 3s2 will excite to the p orbital so that the electron of Cl can be placed in the orbitals. same as in C. but when we add water, lone pair of water will be placed in the d orbital for Si. but in C cannot coz it dont hv d orbital. so that it cant make bond with H in water. dats why SiCl4 get hydrilozed and CCl4 cant.
  • "Reaction with water (hydrolysis) Carbon tetrachloride (tetrachloromethane): Carbon tetrachloride has no reaction with water. If you add it to water, it simply forms a separate layer underneath the layer of water. Suppose a water molecule is going to react with the carbon tetrachloride. The reaction would have to start by the water molecule's oxygen attaching itself to the carbon atom via the oxygen's lone pair. A chlorine atom would get pushed off the carbon in the process. There are two problems with this. First, the chlorines are so bulky and the carbon atom so small, that the oxygen can't easily get at the carbon atom. . . . and even if it did, there will be a stage where there is considerable cluttering around that carbon atom before the chlorine atom breaks away completely. There is going to be a lot of repulsion between the various lone pairs on all the atoms surrounding the carbon. That cluttering is going to make this half-way stage (properly called a "transition state") very unstable. A very unstable transition state means a very high activation energy for the reaction. The other problem is that there isn't a convenient empty orbital on the carbon that the oxygen lone pair can attach to. If it could attach before the chlorine starts to break away, that would be an advantage. Forming a bond releases energy, and that energy would therefore be readily available for breaking a carbon-chlorine bond. But in the case of a carbon atom, that isn't possible. - Silicon tetrachloride: The situation is different with silicon tetrachloride. The silicon atom is bigger, and so there is more room around it for the water molecule to attack, and the transition state will be less cluttered. But silicon has the additional advantage that there are empty 3d orbitals available to accept a lone pair from the water molecule. Carbon doesn't have 2d orbitals because there are no such things. There are no empty 2-level orbitals available in the carbon case. This means that the oxygen can bond to the silicon before the need to break a silicon-chlorine bond. This makes the whole process energetically easier. So . . . silicon tetrachloride reacts violently with water to give white solid silicon dioxide and steamy fumes of HCl. Liquid SiCl4 fumes in moist air for this reason - it is reacting with water vapour in the air." Source and further information: http://www.chemguide.co.uk/inorganic/group4/chlorides.html See also: http://en.wikipedia.org/wiki/Silicon_tetrachloride

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