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![]() The best known boron compound occurring naturally is probably borax, which has the formula of Na 2B 4O 7, with usually a bunch of water molecules attached. When heavier elements are hit by cosmic rays, they can lose a bunch of nuclear particles, forming lighter elements such as B. It is relatively rare, as it is not formed by nuclear fusion in stars, but by cosmic ray spallation. Lets look at Boron and Boron Nitride.ĭensity: Between 2.35 kg/L and 2.52 kg/L, depending on the allotrope.īoron is one of the lighter elements, with atomic number 5. I talked about Nitrogen in Closed Tournament Round 2. Even if Im wrong about that, I dont think the energy of that reaction is nearly as much as that of the first step, so the total procedure is still exothermic. I havent found the energy of the chlorination step, but I am guessing it is slightly exothermic, as the resulting molecule seems more stable. The polymerization of vinyl chloride into PVC releases 105.6 kJ/mol (thats moles of vinyl chloride), enough to need constant cooling. Note that the initiator is not actually a catalyst, as it is used up. A small amount of initiator is required to get the polymerization going. However, in reality it would take two separate steps, first the polymerization of vinyl chloride into PVC and second the actual chlorination. However, as it takes an extra production step to make this stuff, its a bit more expensive.Īs I explained above, this reaction is certainly possible. With the glass temperature over 100 ☌, CPVC can be used to transport nearly boiling water. It is more ductile and it has better heat resistance. The increased chlorine content gives CPVC some advantages over regular PVC. The Cl 2 molecules decompose into Cl radicals, which will replace hydrogens in the PVC. It is made by adding chlorine to PVC and exposing it to UV light. By that time, the chain is many thousands of monomers long.Ĭhlorinated PVC or CPVC is an alternative to PVC. It will react with another vinyl chloride monomer and so on, until the reaction is terminated by pairing up two radicals. At that moment, the other end of the double bond has a spare electron, and we have a new radical. The radical reacts with the vinyl chloride, and using one of the electrons making up the double C=C bond, it binds to a vinyl chloride molecule. A molecule called the initiator produces a radical, a compound that has an unpaired, reactive electron. It is made by polymerizing vinyl chloride, which is done by a so called radical chain reaction. Like most polymers, its exact properties depend on the average chain length of each molecule. Regular PVC is a polymer, a plastic used for water and sewer pipes, among other things. Molecular mass: Varies, but around 100 000 u or more would be a good guess. Melting point: 395 ☌, 743 ☏ (But the glass temperature, at which it becomes soft and rubbery, is around 110 ☌). ![]() ![]() Nowadays, its (almost) exclusively used as an intermediate to make polyvinyl chloride (PVC). Of course, they stopped using the stuff because of its toxicity. In the past, vinyl chloride was used as an aerosol spray propellant, as a refrigerant and according to Wikipedia, even as an inhalational anaesthetic. While this reaction is possible, it takes a lot more effort to keep things under control and not get side-products, so it is not as common. As ethylene is commonly produced from ethane, engineers are looking for ways to produce vinyl chloride directly from ethane in order to reduce costs. Alternatively, with the right catalyst, ethylene will react with chlorine gas. Acetylene can be reacted with HCl gas to form vinyl chloride. It is usually stored as a liquid under pressure. Vinyl chloride is a toxic gas with a sweet smell. Ill talk about the other two compounds here. I discussed the Chlorine radical in Round 8. Note: As The Chem in Rounds 1 4 were written after the tournament, they may refer to later rounds. Part 11: The Chem in SpaceChem - Round 4 The Chem in SpaceChem, Round 4 |