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Calculating Chemical Equations

Calculating Chemical Equations

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Calculating Chemical Equations

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  1. Calculating Chemical Equations Why and How Many Atoms Bond

  2. A Chemical Formula shows how many of which atoms are in a molecule A Subscript is a number placed below and behind a symbol to show how many of which atoms are present H2O Counting Atoms

  3. A Coefficient is placed in front of a molecule to show more than one molecule 3H2O Counting Atoms

  4. A Diatomic Molecule shows two atoms of the same nonmetal (usually in gas form) that have bonded together Reactive nonmetals will bond with one another if no other substance is available for bonding H2 N2 O2 F2 I2 Cl2 Br2 Counting Atoms

  5. A group of atoms that behave as one atom Keep together as a unit Listed on p. 619 If more than one polyatomic ion is present in a molecule, parentheses set it apart Still use a subscript to show how many Ca(OH)2 NH4Cl Polyatomic Ions

  6. Counting Atoms • Write the molecule to be counted • List the participating atoms (or polyatomic ions) under the formula • Write all subscripts, including parentheses • Multiply by the coefficient • Some problems call for a total of atoms, some call for individual atoms

  7. How many total atoms are in Methane, CH4? • 2 • 3 • 4 • 5 • 6

  8. How many atoms of Chlorine are in Carbon Tetrachloride, CCl4? • 2 • 3 • 4 • 5 • 6

  9. How many total atoms are in Magnesium Hydroxide, Mg(OH)2? • 2 • 3 • 4 • 5 • 6

  10. How many atoms of Oxygen are in Acetic Acid, CH3COOH? • 2 • 3 • 4 • 5 • 6

  11. How many total atoms are in Acetic Acid, CH3COOH? • 4 • 5 • 6 • 7 • 8 • 9

  12. Oxidation Numbers • A positive or negative sign used to show what type of ion is formed after an atom has gained or lost enough electrons to be chemically stable • Written like a charge sign (upper right) • Always included with a list of polyatomic ions

  13. BASE OXIDATION NUMBERS BY GROUP +1 0 +2 +3 ±4 -3 -2 -1 USE ROMAN NUMERALS

  14. What is the Oxidation Number for Sulphur (Group 16)? • +1 • +2 • +3 • 4 • -3 • -2 • -1

  15. What is the Oxidation Number for Aluminium (Group 13)? • +1 • +2 • +3 • 4 • -3 • -2 • -1

  16. What is the Oxidation Number for Potassium (Group 1)? • +1 • +2 • +3 • 4 • -3 • -2 • -1

  17. What is the Oxidation Number for Chlorine (Group 17)? • +1 • +2 • +3 • 4 • -3 • -2 • -1

  18. What is used to show the Oxidation Number for Transition Metals (Groups 3 – 12)? • Alchemical Symbols • Transition Icons • Arabic Numerals • Roman Numerals • Hieroglyphics • Kanji

  19. Making formulæ“The Criss-Cross Method” • Write the element with the positive oxidation number • Write the element with the negative oxidation number • Rewrite the two symbols together below the symbols with their oxidation number • Drop the positive or negative sign • Write the oxidation number from one symbol on the other symbol as a subscript • Remember to add parentheses for polyatomic ions • Don’t write “1”s • Reduce any evenly-divisible subscripts

  20. What is the correct formula for a bond between Carbon and Hydrogen? • CH • C2H2 • CH3 • C2H3 • CH4

  21. What is the correct formula for a bond between Sodium and Nitrogen? • NaN • Na2N2 • Na3N • Na2N3 • Na3N4

  22. What is the correct formula for a bond between Calcium and Chlorine? • CaCl • Ca2Cl2 • Ca2Cl • CaCl2 • Ca3Cl4

  23. What is the correct formula for a bond between Sodium and Hydroxide? • NaOH • Na(OH)2 • Na(OH)3 • Na2(OH)3 • Na(OH)4

  24. What is the correct formula for a bond between Aluminum and Sulfate? • AlSO4 • Al2(SO4)2 • Al2(SO4)3 • Al3(SO4)3 • Al(SO4)4

  25. Binomial Nomenclature • Naming a two-part name • Used to differentiate between Fluorine (an element) and Fluoride (part of a compound) • Never change the name of a Polyatomic Ion • Big difference between Sulfide and Sulfite

  26. Ionic Compounds • List the positive ion (or metal) first • Use Roman Numerals to show the Oxidation number of a transition metal • Begin the negative ion (or nonmetal), changing the ending to –ide • Oxide • Sulfide • Phosphide

  27. Covalent Compounds • Prefixes are used to show how many of which atoms • Prefixes are number-words from Greek & Latin • Write the name of the first atom • Add a prefix only if there is more than one of the first • Write the name of the second atom • Add a prefix showing how many of the second are present • Change the ending to -ide

  28. 1 – Mono- 2 – Di- 3 – Tri- 4 – Tetra-, 5 – Penta- 6 – Hexa- 7 – Hepta- 8 – Octa- 9 – Nona- 10 – Deka- Numbering Prefixes

  29. What is the name for N2O4? • Nitrogen Oxide • Dinitrogen Oxide • Dinitrogen Dioxide • Dinitrogen Tetraoxide • Nioxx (Nioxalate)

  30. What is the name for Na2S? • Sodium Sulfide • Sodium Sulfite • Sodium Sulfate • Disodium Sulfide • Disodium Sulfate

  31. What is the name for CO2? • Carbon Oxide • Carbon Dioxide • Monocarbon Oxide • Monocarbon Dioxide • Mi-Bref (B-hot)

  32. What is the name for (NH4)2O? • Nitrogen Hydrogen Oxide • Mononitrogen Tetrahydrogen Oxide • Ammonium Oxide • Diammonium Oxide • Ammonium Oxalate

  33. Chemical Equations • A shorthand way to describe a chemical reaction using chemical symbols and formulæ

  34. Chemical Equations • Has three parts • Reactants • Substances present before the reaction • Products • Substances present after the reaction • Yield Arrow • Indicates the direction of a reaction • Some reactions are reversible

  35. Writing a Chemical Equation Chemical symbols give a “before-and-after” picture of a chemical reaction Reactants Products MgO + C CO + Mg magnesium oxide to form carbon monoxide reacts with carbon and magnesium

  36. Balancing Chemical Equations • Equations must be balanced to observe the Law of Conservation of Matter • Matter can not be created or destroyed under normal reactions • If you begin a reaction with 5 g of Hydrogen, you must end up with 5 g of Hydrogen

  37. A Balanced Chemical Equation Same numbers of each type of atom on each side of the equation Al + S Al2S3 Not Balanced 2Al + 3S Al2S3Balanced

  38. Balancing Chemical Equations • Count atoms on both sides of the yield arrow • Determine which elements are unequal • Use coefficients to balance the number of atoms on both sides • If you multiply one element in a compound, you multiply both elements in a compound • You can treat Polyatomic Ions as one if they appear on both sides of the equation • Go for the highest unequal elements first • Leave solitary elements for last

  39. Steps in Balancing An Equation Fe3O4 + H2 Fe +H2O Fe:Fe3O4 + H23 Fe +H2O O:Fe3O4 + H2 3 Fe +4H2O H: Fe3O4 + 4 H2 3 Fe +4H2O

  40. Balancing Chemical Equations Mg + N2 Mg3N2 Al + Cl2 AlCl3

  41. Balancing Chemical Equations Fe2O3 + C Fe + CO2 Al + FeO Fe + Al2O3 Al + H2SO4 Al2(SO4)3 + H2

  42. Types of Chemical Reactions • Synthesis • Two or more substances form one new substance H2 + O2  H2O N2 + H2  NH3

  43. Types of Chemical Reactions • Decomposition • One substance breaks down to form two or more new substances PbCO3  PbO + CO2 H2CO3  H2O + CO2

  44. Types of Chemical Reactions • Single Displacement • One substance replaces another in a compound Li + AlCl3  LiCl + Al

  45. Types of Chemical Reactions • Double Displacement • Two substances “swap partners” in two compounds KOH + HBr  KBr + H2O NaOH + H2CO3  Na2CO3 + H2O

  46. Types of Chemical Reactions • Neutralization • Double-displacement reaction where an acid and a base form a salt and water KOH + HBr  KBr + H2O NaOH + H2CO3  Na2CO3 + H2O

  47. Acids and Bases • Acids • Taste Sour • Have a pH of less than 7 • Produce Hydronium H3O+1 in solution • Have an “extra” H- on the beginning of the formula H2SO4 – (Hydro)Sulfuric Acid H3PO4 – (Hydro)Phosphoric Acid HNO3 – (Hydro)Nitric Acid HCl – Hydrochloric Acid

  48. Acids and Bases • Bases • Taste bitter • Have a pH of more than 7 • Produce Hydroxide OH–1 in solution • Have an –OH on the end of the formula NaOH – Sodium Hydroxide KOH – Potassium Hydroxide Ca(OH)2 – Calcium Hydroxide NH4OH– Ammonium Hydroxide

  49. Types of Chemical Reactions • Combustion • Where a carbon compound combusts with oxygen gas to form carbon dioxide and water CH4 + O2  CO2 + H2O C2H6 + O2  CO2 + H2O

  50. Change in ENERGY • Every reaction has some change in energy • Two possibilities: