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Combination combustion decomposition
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Combination combustion decomposition

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  • 1. 10/4/2010 Combination Combustion Decomposition Combination Reactions • A + B AB • A and B can be elements or compounds! • What to look for – 2 or more separate reactants, forming 1 product 1
  • 2. 10/4/2010 • Some of these reactions will have links to watch videos • Products of metal and non-metal – often you can determine formula from group # or typical charge Zn + I2 ZnI2 The reaction is exothermic, the Heat released sublimes the excess Elemental iodine!! The reaction requires a bit of water To “catalyze” or initiate the reaction Zinc metal is silvery, iodine is magenta crystals, the zinc iodide in a white salt Zinc always forms +2 ions so ZnI2 is expected to be the product 2
  • 3. 10/4/2010 Dropping flakes of Antimony, a “semi-metal” Into chlorine gas initiates An energetic reaction As evidenced by the “sparks” H2 + Cl2 2 HCl This reaction is Initiated by light from Burning Mg and Produces an explosion 3
  • 4. 10/4/2010 Note: properties change – iron is magnetic – but iron(III) sulfide is not!! Na + Cl2 2 NaCl This reaction also Needs to be initiated with Water 4
  • 5. 10/4/2010 Combustion reactions • All of us should be familiar with combustion – Using a charcoal grill C + O2 CO2 – Using a butane lighter C4H10 + O2 CO2 + H2O – Using a “gas” grill C3H8 + O2 CO2 + H2O – Driving a gasoline car C8H18 + O2 CO2 + H2O • The common thread in all these reactions is elemental oxygen (O2) – they all produce heat and light • PS – the above equations are not necessarily balanced – can you balance them?? Combustion reaction • Reaction with oxygen • A + O2 AO (also could be combination) • AB + O2 AO + BO • What to look for – oxygen (O2) as a reactant, all products are oxides 5
  • 6. 10/4/2010 Combination/Combustion example • H2 from Zn/HCl rx balloon • Clear away all combustible, have a wash bottle ready • Add energy (reaction is not spontaneous at room temperature) • Light wooden splint, hold with crucible tongs • Touch bottom of balloon – be ready! Combination products • Metal + non-metal: use typical charges!!! For product!!! 6
  • 7. 10/4/2010 Combustion or combination Combustion 7
  • 8. 10/4/2010 Note –more than one product, oxygen part of both products, O2 is a reactant Complete combustion of carbon containing compounds produces CO2 not CO Combination/Combustion • O2 is a reactant and product contains O • 2+ reactants, 1 product 8
  • 9. 10/4/2010 Or combination!!! O2 MgO Mg Note,Mg+2 smaller, O-2 larger than elemental Atoms!!! 9
  • 10. 10/4/2010 Decomposition • AB -> A + B • What to look for : 1 reactant, 2 or more products Decomposition example • Catalytic decomposition of hydrogen peroxide (H2O2) • ½ full test tube hydrogen peroxide • Add ~ ½ t yeast • Mix with glass stirring rod • What happens, what is produced? 10
  • 11. 10/4/2010 Hydrogen peroxide decomposition • H2O2(aq) H2O(l) + O2(g) • Catalyst – catalase, peroxidase – found in blood, radishes, red beets, potatoes! • You can try this reaction – get a slice of raw potato, radish or red beet and pour a few drop of hydrogen peroxide (3%) on it – do you see bubbles --- you may have used this on cut with the same effect!! • Note demonstration with higher concentration 11
  • 12. 10/4/2010 2 NI3 N2 + 3I2 2 H2O 2 H2 + O2 Need electrolyte!! 12
  • 13. 10/4/2010 2 HgO Hg + O2 HgO Hg Heat applied cinnabar 13