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Chemical reactions

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  1. Chemical reactions • Remember indications of a chemical change • energy change • Color change • Precipitate formed • Gas given off

  2. What is energy? • Anything that is not matter and can cause a change in matter • Examples: • Heat • Sound • light

  3. Symbols to know  yields or reacts to form + plus or and (s) solid (l) liquid (g) gas (aq) dissolved in water catalyst is written on yields sign Heat is a triangle on yields sign

  4. Remember • Ionic compounds are usually solids (s) (but they can be dissolved in water) • All acids are dissolved in water (aq) • Metals are solid except Hg • Br2 is a liquid

  5. Magnesium metal and sodium chloride dissolved in water react to form magnesium chloride dissolved in water and sodium metal

  6. Try these! • Solid magnesium reacts with oxygen in the air to form solid magnesium oxide. • Bubbles of hydrogen gas and aqueous zinc sulfate are produced when zinc metal is added to sulfuric acid

  7. Diatomic molecules H2N2 O2 F2 Cl2 Br2 I2

  8. Law of Conservation of Matter matter cannot be created nor destroyed (its conserved). • number of atoms reacted equals number of atoms produced • take an atom inventory

  9. Rules for Balancing Equations 1.Write reactants on left, products on right 2 Write correct formulas 3. Take an atom inventory • Balance the number of atoms by placing a coefficient in front of the formula (DON’T CHANGE SUBSCRIPTS) 5. Repeat until all atoms are balanced 6. Put coefficients in lowest terms

  10. Practice • Balance and write the words: Br2(l) + NaI(aq) NaBr(aq) + I2(s) Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)

  11. Practice • Mercury metal is produced by heating a mixture of mercury(II)sulfide and calcium oxide. Other products are calcium sulfide and calcium sulfate.

  12. Types of Chemical reactions • Combination(synthesis) A + B  AB • Decomposition AB A + B • Single replacement A + BX  AX + B • Double Replacement AX + BYAY + BX • Combustion HxCy + O2  CO2 + H2O

  13. Combination(synthesis) Mg + O2  MgO Sodium and chlorine react to form Iron and oxygen react to form iron (III) product

  14. Decomposition H2O2 H2O + O2 Water decomposes with electricity Into its elements Calcium carbonate decomposes to form calcium oxide and carbon dioxide

  15. Tin Sn+2,Sn+4 Hydrogen H+

  16. Single replacement Mg + HCl MgCl2 + H2 look up on activity series(p106) Mg must be higher than H for a reaction Mg + KCl No reaction Mg is lower than K so “ no go”

  17. Activity Series and History • What were some of the first metals used by man? • Copper age @5 –4000 BC • Why? • What age came next? • Bronze age 3 – 2000 BC (Trojan war) • What is bronze? • What age came next? • Iron Age 1000 BC on

  18. Li K Ba Sr Ca Na Mg Al Mn Zn Fe Cd Co Ni Sn Pb H Cu Ag Hg Au Why Bother Discussing This? • Locate copper, tin and iron • Copper is found in metallic form • It is an uncombined element • Look below copper, gold, mercury and silver • “coinage” metals • Tin is easy to turn into its elemental form • Iron requires lots of energy!

  19. Ionic Compounds • When an ionic compound dissolves in water, what actually happens?

  20. The battle between water and “columbic” attraction • Particles of opposite charge are attracted to each other. • This attraction is called columbic attraction

  21. Ionic Solution • So an ionic solution is really a bunch of charged particles floating around • Water “hydrates” or surrounds each particle • Water keeps the Plus and minus charges from attracting each other • If the plus and minus are more attracted to each other than to the water, then they combine and make a precipitate - it is not soluble

  22. Double Replacement • Metal ions replace each other • All reactants are aqueous • Check products on solubility table to see if solid or aqueous MgSO4 + NaCl BaSO4 + Ag2CO3 

  23. Combustion • Complete hydrocarbon + O2 CO2 + H2O C5H10 + O2  CO2 + H2O • Incomplete Hydrocarbon + O2  CO + H2O C + H2O

  24. Practice • Balance and write the words: Br2(l) + NaI(aq) NaBr(aq) + I2(s) Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)

  25. Practice • Balance and write the words: Br2(l) + NaI(aq) NaBr(aq) + I2(s) Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)

  26. Practice • Balance and write the words: Br2(l) + NaI(aq) NaBr(aq) + I2(s) Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)

  27. C + O2 CO2 C-1 O-2 C- 1 O – 2