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Na & K , Mg & Br

Na & K , Mg & Br. Zephan and Tae. Alkali Metals. Most reactive elements Ionic in nature (solid or aqueous) Kept under special conditions to prevent contact with air. Na + and K + dominate alkali metals. Sodium. Primarily NaCl or halite.

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Na & K , Mg & Br

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  1. Na & K , Mg & Br Zephan and Tae

  2. Alkali Metals • Most reactive elements • Ionic in nature (solid or aqueous) • Kept under special conditions to prevent contact with air. • Na+ and K+ dominate alkali metals

  3. Sodium • Primarily NaCl or halite. • Major production from mining salt deposits formed from millions of years of evaporation. • Also produced by the evaporation of concentrated salt solutions called Brines.

  4. Brines • After evaporation, the solid is melted to use in an electrolytic cell called the Down’s cell. • Molten Na and Ca forms at the cathode. • Calcium used to lower the boiling point of the sodium chloride. • Na is siphoned off by a collection pipe at the cathode and Cl collected at the anode. • Sodium and Chlorine are kept separate by an Iron screen to prevent explosive recombining.

  5. Potassium • Most potassium comes from sylvite, KCl. • Too soluble to be produced by the same methods as sodium. • Instead liquid sodium is used to reduce K+. • Na(l) + K+(l) -> Na+(l) + K(g) • This works because the sodium atom is smaller than the potassium atom so it has greater electron affinity and electronegativity. • This reaction is raised to 850OC, beyond the boiling point of potassium. to push the reaction to products. • K(g) is then collected, which pushes the reaction even more to products to make this an efficient reaction.

  6. Potassium (saltpeter, KNO3) in gunpowder and fireworks

  7. Jet Engines • Not really. • Sodium and Lead were once used to make antiknock additives in gasoline to increase the fuel’s octane rating. • Example: Tetraethyl lead or leaded gas. • 4C2H5Cl(g) + 4Na(s) -> (C2H5)4Pb(l) + 4NaCl(s) • Because of the toxicity of lead and its’ effects on the environment, leaded fuels are now only used in piston-based aircraft engines.

  8. Nuclear Reactors Sodium can be used in a type of nuclear reactor called a breeder reactor. • Breeder reactor means it creates more usable material than it consumes. • Low melting point, high viscosity, thermal conductivity, and heat capacity make sodium perfect for cooling reactors. • Potassium is also used in chemical and nuclear reactors as an alloy with sodium to be used as a heat exchanger. • Chemical reactors are containers designed to increase the efficiency of a reaction by applying or removing heat, pressure, agitation, etc.

  9. References • http://www.vanderkrogt.net/elements/images/sodium.jpg • http://www2.ulg.ac.be/lem/images/cesium.jpg • http://www.pakwheelers.com/gallery/2007/7/27/Khewra_Salt_Mines__Punjab_UXRKZ1.jpg • http://wps.prenhall.com/wps/media/objects/602/616516/Media_Assets/Chapter18/Text_Images/FG18_16.JPG • http://upload.wikimedia.org/wikipedia/commons/d/df/Pyrodex_powder_ffg.jpg • http://image18.webshots.com/18/3/66/89/215336689dflqEn_ph.jpg • http://farm4.static.flickr.com/3285/2863252872_caa0fa795a.jpg • http://farm1.static.flickr.com/28/36086837_b0f6ed5961.jpg?v=0 • http://www.emeraldinsight.com/fig/2730090605002.png

  10. Mining the sea: Mg and Br • Magnesium(Mg) - The eighth most abundant element found on the Earth ( About 0.13% of MgCl2 is present in seawater) - Strong reducing agent (Can not be obtained by chemical reduction method)

  11. Extraction of Mg - Many methods are available from its ores - Dow process (the most widely used method from seawater)

  12. Dow process Seashell Seawater 1. Mining -Intake of Seawater (Mg2+) - Ca(OH)2 from seashells Seashells(CaCO3) decomposed with heat to CaO and mixed with waterCa(OH)2 2. Converting to mineral Ca(OH)2(aq) + Mg2+(aq)  Mg(OH)2(s) + Ca2+(aq) 3. Converting to compound Mg(OH)2(s) + 2HCl(aq)  MgCl2(aq) + 2H2O(l) 4. Evaporation 5. Electrochemical redox MgCl2(l)  Mg(l) +Cl2(g) (heating above 700℃) Mg(OH)2 Setting tank Filters HCl MgCl2 Evaporation Dryer MgCl2*nH2O Mg(s) Cl2(g) Electrolysis

  13. Uses of Magnesium - In the manufacture of light and high-tensile alloys as form of alloy - Sacrificial anodes - In the metallurgical extraction of other metals ( Be, Ti, Zr and U)

  14. Bromine (Br) • A member of the halogen group • Liquid nonmetalic element • The largest source of Br is the oceans as Br- (at concentration of 0.065g/L) - Readily oxidized to Br2 with Cl2(aq) at standard state 2Br-(aq) + Cl2(aq)  Br2(l) +2Cl-(aq), ∆Go = -61.5KJ

  15. AlsoSmall amounts of bromine can be made through the reaction with Sulphuric acid (H2SO4) NaBr (s) + H2SO4(l)  HBr (g) + NaH2SO4(s) 2HBr (g) + H2SO4(l)  Br2(g) + SO2 (g) + 2H2O (l)

  16. Uses of Bromine - In making fire retardant chemicals - In water purification as a disinfectant - In photography film (inorganic bromine) AgBr - In medicines - As a petrol additive to prevent lead being deposited in the cylinders (Anti-knock agent)

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