Section 9: Halogens And Halogen Compounds

SECTION 9 : HALOGENS AND HALOGEN COMPOUNDS 1. Fluorine and its Compounds Fluorine is the most abundant and most reactive in nature. Fluorine is found in the minerals fluorspar (CaF2 ), cryolite (Na3 AlF6 ), and flouroapatite (Ca5(PO4)3 \F). Apart from that, this element is found in human and animal teeth, although in low levels. Fluorine can be obtained using the Moissan process, after the name of the person who first isolated fluorine, H. Moissan (1886). This process uses the electrolysis method of dissolved HF in melted KHF2 . Reaction: 2HF H2 (g) + F2 (g) F2 is stored in a Ni or Cu container, because the surface of the metal container will form a protective layer of fluoride. Uses of fluorine compounds include: a. CCl2F2 (freon-12), used as a refrigerant in refrigerators and air conditioning. b. Na2SiF6 , when mixed with toothpaste will function to strengthen teeth. c. NaF, can be used in the processing of uranium isotopes, namelynuclear reaction fuel. d. Teflon, a heat-resistant plastic material. e. Hydrofluoric acid is used to engrave (sketch) glass because it can react with glass. 2. Chlorine and its compounds Chlorine is contained in sea water in the form of salt (NaCl) at a level of 2.8%. The oxidizing properties that are not as strong as F2 mean that chlorine can be produced using electrolysis or oxidation. Chlorine can be made using several methods, namely: a. Deacon Process (oxidation) HCl is mixed with air, then flowed through CuCl 2 which acts as a catalyst. The reaction occurred at a temperature of ± 430 °C and a pressure of 20 atm. b. Electrolysis of NaCl solution using a diaphragm Reaction: 2 NaCl + 2 H2O c. Electrolysis of molten NaCl Reaction: 2 NaCl + The uses of chlorine compounds include:  Cl2 , used as a disinfectant to kill germs that can cause various diseases.  NaCl, used as table salt.  KCl, used for fertilizer.  NH4Cl, used as a battery charging electrolyte.  NaClO can oxidize dyes (bleach), so it can be used as a bleaching agent, namely oxidizing dyes.  Chlorine (Ca(OCl)2 ), is used as a disinfectant in water.  ZnCl2 , as a brazing or solder material.  PVC, used in the plastic industry for pralon pipes.  Chloroform (CHCl3 ), used as a solvent and anesthetic insurgery. 3. Bromine and its compounds Bromine can be found in sea water. Bromine does not have oxidizing propertiesoverpowering. Bromine can be obtained in several ways.On an industrial scale, bromine is produced by extracting seawater. This is because the Br content in sea water will be high (approximately 70 ppm). First, the pH of seawater is made to 3.5 and then reacted with Cl2 (g) to oxidize Br– to Br2 (g). Reaction: Cl2 (g) + 2 Br– (aq) Br2 (g) + 2 Cl– (aq) Uses of bromine compounds include:  NaBr, as a nerve sedative.  AgBr, for photographic film. AgBr is dissolved in the gelatin film, then the film is washed with Na2S2O3 solution to remove excess AgBr, so that silver will remain on the film as a black shadow.  CH3Br, as a mixture of fire extinguishing agents.  C2H4Br2 , added to gasoline so that lead (Pb) in gasoline does not precipitate because it is converted into PbBr2 . 4. Iodine and its compounds The most commonly found iodine compound is NaNIO3 which is mixed with NaNO3 . Even though iodine is solid, it sublimes easily because it has a high vapor pressure. On an industrial scale, iodine is obtained by reacting NaIO3 with sodium bisulfite (NaHSO3 ). The I2 precipitate obtained is filtered and purified. Reaction: 2 NaIO3 + 5 NaHSO3 3NaHSO4 + 2 Na2SO4 + H2O + I2 Uses of iodine compounds include:     I2 in alcohol, used as an antiseptic for wounds to prevent exposure infection. KIO3 , as an addition to iodine in table salt. I2 , used to test starch in the flour industry. NaI, when added to table salt, can be used to reduce iodine deficiency which can cause goiter.  Iodoform (CHI3 ), as a disinfectant to treat ulcers.