Reactions & Formulas

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Reactions & Formulas

  1. 1. + - + + - + - + + - Reactions & Formulas Introductory Chemistry Canadian Academy MrT draft presentation – to be updated
  2. 2. The magnesium is combusting. The magnesium is combining with oxygen.There is a physical change but not achemical change. 2
  3. 3. Reactions & FormulasAssessment Statements • Name simple ionic and covalent compounds from their formula. • Write formulas for simple ionic and covalent compounds based on their name. • Write word equations for reactions. • Identify reactants and products in reactions. • Apply state symbols to equations. • Balance simple formula equations. • Identify characteristics of reactions: • ∆ colour • ∆ temperature (exothermic or endothermic) • precipitate formation • gas production • ∆ pH • Use conditions for reactions appropriately above the arrow in the equation (heat, catalyst etc). • Recognise six types of reaction: synthesis, decomposition, single replacement, double replacement, combustion and neutralisation.
  4. 4. 1 2 13 14 15 16 17 18+1 +2 -3 -2 -1 non-metals Periodic table from: http://www.elementsdatabase.com/
  5. 5. +1 +2 -3 -2 -1 non-metals http://commons.wikimedia.org/wiki/Periodic_Table_of_Elements
  6. 6. How do we know a reaction has taken place? • ∆ colour (∆ = ‘change in’) • ∆ temperature (exothermic or endothermic) • ∆ pH • precipitate formation • gas production Which of these signs of a chemical reaction have we come across in our reactions so far?
  7. 7. Naming IonsRemember: metals bonding withnon-metals form ionic bonds.Some ions are polyatomic. Thismeans they are made of groupsof atoms which stay together inreactions – such as carbonates.What do the elemental anionshave in common in their name?What do the polyatomic anionshave in common in their name(except hydroxide)?What is the difference betweenthe iron (II) and iron (III) ions?
  8. 8. Naming Ionic CompoundsRules:• balance the charges• keep polyatomic ions togetherExamples:HCl hydrogen chlorideNaOH sodium hydroxideZnCl2 zinc chlorideFe2O3 iron oxideNaOH sodium hydroxidePb(NO3)2 lead nitrate
  9. 9. Naming Covalent Molecules Remember: You can only correctly call it a molecule if it is covalently-bonded. Covalent bonds form between non-metal atoms. Name the compound this way: • You don’t need mono- if the first atom is single • Use the prefixes for all other atoms Examples: CO carbon monoxide CO2 carbon dioxide N2O3 dinitrogen trioxide CF4 N2O4 N2H4 H2O
  10. 10. Conventions in Writing Reactions reactants products conditions for reaction to occur (e.g. heat, catalysts) symbol equation Mg (s) + O2 (g) heat MgO (s) magnesium + oxygen magnesium oxide “gives” word equation State symbols need to be included: (s) solid – this included precipitates (g) gas (l) liquid (aq) aqueous solution: solutes dissolved in water state symbols should be subscripted
  11. 11. Wait! The reactants and products are not balanced Mg (s) + O2 (g) heat MgO (s) magnesium + oxygen magnesium oxide
  12. 12. Balancing Equations The Law of Conservation of Mass states that matter is neither created nor destroyed. There MUST be the same number of atoms on each side of the equation. Mg (s) + O2 (g) heat MgO (s) magnesium + oxygen magnesium oxide Reactants Products Mg 1 1 O 2 1 Simple steps for balancing equations: 1. List & count the elements and groups on each side of the equation. Don’t split polyatomic ions. 2. Select the compound with the greatest number of atoms (not counting H and O). 3. Balance the atoms in this compound on both sides of the equation. 4. Don’t change any compounds. 5. Balance any groups, such as polyatomic ions. 6. Finish up with H and O.
  13. 13. Balancing Equations The Law of Conservation of Mass states that matter is neither created nor destroyed. There MUST be the same number of atoms on each side of the equation. Mg (s) + O2 (g) heat 2MgO (s) magnesium + oxygen magnesium oxide Reactants Products Mg 1 1 2 O 2 1 2 Simple steps for balancing equations: 1. List & count the elements and groups on each side of the equation. Don’t split polyatomic ions. 2. Select the compound with the greatest number of atoms (not counting H and O). 3. Balance the atoms in this compound on both sides of the equation. 4. Don’t change any compounds. 5. Balance any groups, such as polyatomic ions. 6. Finish up with H and O.
  14. 14. Balancing Equations The Law of Conservation of Mass states that matter is neither created nor destroyed. There MUST be the same number of atoms on each side of the equation. 2Mg (s) + O2 (g) heat 2MgO (s) magnesium + oxygen magnesium oxide Reactants Products Mg 1 2 1 2 O 2 1 2 Two molecules of Mg are needed to react with one molecule of O2, giving 2 MgO. Simple steps for balancing equations: 1. List & count the elements and groups on each side of the equation. Don’t split polyatomic ions. 2. Select the compound with the greatest number of atoms (not counting H and O). 3. Balance the atoms in this compound on both sides of the equation. 4. Don’t change any compounds. 5. Balance any groups, such as polyatomic ions. 6. Finish up with H and O.
  15. 15. Types of Reactions A+B AB AB A+B replacement replacement double single AB + C CB + A AB + CD AD + BC heat H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2O
  16. 16. Synthesis ReactionsThese can be simplified as A + B  ABWhere two or more reactants combine to make a single product. + CO2 + H2O H2CO3 (g) (l) (aq) carbon dioxide + water carbonic acid Reactants Products balanced? C O H
  17. 17. Synthesis ReactionsThese can be simplified as A + B  ABWhere two or more reactants combine to make a single product. + CO2 + H2O H2CO3 (g) (l) (aq) carbon dioxide + water carbonic acid Reactants Products balanced? C 1 1 O 3 3 H 2 2
  18. 18. Types of Reactions A+B AB AB A+B replacement replacement double single AB + C CB + A AB + CD AD + BC heat H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2O
  19. 19. Decomposition ReactionsThese can be simplified as AB  A + BWhere a single reactant breaks down into component elements or compounds. + MnO2 H2O2 H2O + O2 (l) (l) (g) hydrogen peroxide water + oxygen MnO2 acts as a catalyst in this reaction. It allows the reaction to take place more quickly but is not used up. We put it above the arrow. It can be recovered and reused in another reaction. MnO2
  20. 20. Decomposition ReactionsThese can be simplified as AB  A + BWhere a single reactant breaks down into component elements or compounds. + MnO2 H2O2 H2O + O2 (l) (l) (g) hydrogen peroxide water + oxygen MnO2 acts as a catalyst in this reaction. It allows the reaction to take place more quickly but is not used up. We put it above the arrow. It can be recovered and reused in another reaction. MnO2
  21. 21. Decomposition ReactionsThese can be simplified as AB  A + BWhere a single reactant breaks down into component elements or compounds. + MnO2 H2O2 H2O + O2 (l) (l) (g) hydrogen peroxide water + oxygen MnO2 acts as a catalyst in this reaction. It allows the reaction to take place more quickly but is not used up. We put it above the arrow. It can be recovered and reused in another reaction. Enzymes are catalysts found in living organisms. They are proteins with an active site. MnO2
  22. 22. Decomposition ReactionsThese can be simplified as AB  A + BWhere a single reactant breaks down into component elements or compounds. + MnO2 H2O2 H2O + O2 (l) (l) (g) hydrogen peroxide water + oxygen Reactants Products balanced? O H
  23. 23. Decomposition ReactionsThese can be simplified as AB  A + BWhere a single reactant breaks down into component elements or compounds. + MnO2 H2O2 H2O + O2 (l) (l) (g) hydrogen peroxide water + oxygen Reactants Products balanced? O 2 3 H 2 2
  24. 24. Decomposition ReactionsThese can be simplified as AB  A + BWhere a single reactant breaks down into component elements or compounds. + MnO2 H2O2 (l) 2H2O + (l) O2 (g) hydrogen peroxide water + oxygen Reactants Products balanced? O 2 3 4 H 2 2 4
  25. 25. Decomposition ReactionsThese can be simplified as AB  A + BWhere a single reactant breaks down into component elements or compounds. + 2H2O2 MnO2 2H2O + O2 (l) (l) (g) hydrogen peroxide water + oxygen Reactants Products balanced? O 2 4 3 4 H 2 4 2 4
  26. 26. Decomposition ReactionsThese can be simplified as AB  A + BWhere a single reactant breaks down into component elements or compounds. Heat Heat CuSO4.5H2O CuSO4 + 5H2O (g) (s) (s) copper (II) sulphate pentahydrate copper (II) sulphate + water
  27. 27. Decomposition ReactionsThese can be simplified as AB  A + BWhere a single reactant breaks down into component elements or compounds. Heat + Heat CuSO4.5H2O CuSO4 + 5H2O (g) (s) (s) copper (II) sulphate pentahydrate copper (II) sulphate + water
  28. 28. 28
  29. 29. Danger: dihydrogen monoxide! Lethal if inhaled. Found in disaster zones. Reduces the effectiveness of brakes. Found in tumour cells, viruses and deadly bacteria. Contributes to electrocutions. Used by terrorists and pirates. Find out more about this lethal substance: http://www.dhmo.org/facts.html
  30. 30. Ionic Covalent• Don’t use mono-, di- etc in prefixes. • Endings usually –ide.• Cation, then anion • Don’t need mono- prefix for first e.g. lithium bromide. atom if it is single (e.g. CH4)• Don’t break up polyatomic ions. • Name in order of the periodic table, but H is before ORemember that in ionic compounds,the sum of the charges must be zero.Therefore sodium sulphide is Na2S, notNaS. 30
  31. 31. Types of Reactions A+B AB AB A+B replacement replacement double single AB + C CB + A AB + CD AD + BC heat H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2O
  32. 32. Combustion ReactionsThis is the combustion (burning) of a hydrocarbon (contains C and H), in oxygen.Complete combustion results in the products water and carbon dioxide. CxHx () + O2 (g) heat CO2 + H2O (g) (g) hydrocarbon + oxygen carbon dioxide + water e.g CH4 (g) + O2 (g) heat CO2 + H2O (g) (g) methane + oxygen carbon dioxide + water Reactants Products C 1 1 O 2 3 H 4 2
  33. 33. Combustion ReactionsThis is the combustion (burning) of a hydrocarbon (contains C and H), in oxygen.Complete combustion results in the products water and carbon dioxide. CxHx () + O2 (g) heat CO2 + H2O (g) (g) hydrocarbon + oxygen carbon dioxide + water e.g CH4 + O2 (g) heat CO2 +2H2O (g) (g) (g) methane + oxygen carbon dioxide + water Reactants Products C 1 1 O 2 3 4 H 4 2 4
  34. 34. Combustion ReactionsThis is the combustion (burning) of a hydrocarbon (contains C and H), in oxygen.Complete combustion results in the products water and carbon dioxide. CxHx () + O2 (g) heat CO2 + H2O (g) (g) hydrocarbon + oxygen carbon dioxide + water e.g CH4 (g) + 2O2 (g) heat CO2 +2H2O (g) (g) methane + oxygen carbon dioxide + water Reactants Products C 1 1 O 2 4 3 4 H 4 2 4
  35. 35. Combustion ReactionsA chemical reaction is taking place at the gas tap! C3H8 (g) + O2 (g) heat CO2 + H2O (g) (g) propane + oxygen carbon dioxide + water Which product of one of the reactions we’ve carried out already could be used to test if the condensation really is water? Is propane a covalent or ionic compound? What’s an alternative name for propane, based on the naming conventions we have just learned?
  36. 36. Combustion ReactionsA chemical reaction is taking place at the gas tap! C3H8 (g) + O2 (g) heat CO2 + H2O (g) (g) propane + oxygen carbon dioxide + water Is it balanced? Reactants Products C O H
  37. 37. Combustion ReactionsA chemical reaction is taking place at the gas tap! C3H8 (g) + O2 (g) heat CO2 + H2O (g) (g) propane + oxygen carbon dioxide + water Is it balanced? Reactants Products C 3 1 O 2 3 H 8 2
  38. 38. Combustion ReactionsA chemical reaction is taking place at the gas tap! C3H8 (g) + O2 (g) heat 3CO2 (g) + H2O (g) propane + oxygen carbon dioxide + water Is it balanced? Reactants Products C 3 1 3 O 2 3 6 H 8 2
  39. 39. Combustion ReactionsA chemical reaction is taking place at the gas tap! C3H8 (g) + O2 (g) heat 3CO2 +4H2O (g) (g) propane + oxygen carbon dioxide + water Is it balanced? Reactants Products C 3 1 3 O 2 3 6 10 H 8 2 8
  40. 40. Combustion ReactionsA chemical reaction is taking place at the gas tap! C3H8 (g) +5O2 (g) heat 3CO2 +4H2O (g) (g) propane + oxygen carbon dioxide + water Is it balanced? Reactants Products C 3 1 3 O 2 10 3 6 10 H 8 2 8
  41. 41. Combustion Reactions Do NOT try these at home.Alcohols will also go through combustion reactions._CH3OH(l) + _O2(g) heat ___ (g) + ____ (g) methanol + oxygen carbon dioxide + water http://www.youtube.com/watch?v=SJCcH0ATMQ4
  42. 42. Combustion Reactions Do NOT try these at home.Alcohols will go through combustion reactions._CH3OH(l) + _O2(g) heat _CO2(g) + _H2O(g) methanol + oxygen carbon dioxide + water Balance it! Reactants Products C 1 1 O 3 3 H 4 2
  43. 43. Combustion Reactions Do NOT try these at home.Alcohols will go through combustion reactions.2CH3OH(l) + 3O2(g) heat 2CO2(g) + 4H2O(g) methanol + oxygen carbon dioxide + water Balance it! Reactants Products C 1 2 1 2 O 3 8 3 8 H 4 8 2 8
  44. 44. Types of Reactions A+B AB AB A+B replacement replacement double single AB + C CB + A AB + CD AD + BC heat H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2O
  45. 45. Single- & double-replacement and neutralisation reactions HCl & NaOH universal indicator HCl AgNO3 NaCl H2O HCl CuSO4 NaHCO3 Mg Fe Two white solids. Which is PbNO3 and which is KI? 45
  46. 46. Single Replacement ReactionsThese can be simplified as AB + C  A + BCWhere an element trades places with another element in a compound. + - + + - + HCl + Mg MgCl2 + H2 (aq) (s) (aq) (g) hydrogen peroxide magnesium chloride + hydrogen Reactants Products balanced? Cl Mg H
  47. 47. Single Replacement ReactionsThese can be simplified as AB + C  A + BCWhere an element trades places with another element in a compound. + - + + - + HCl + Mg MgCl2 + H2 (aq) (s) (aq) (g) hydrogen peroxide magnesium chloride + hydrogen Reactants Products balanced? Cl 1 2 Mg 1 1 H 1 2
  48. 48. Single Replacement ReactionsThese can be simplified as AB + C  A + BCWhere an element trades places with another element in a compound. + - + + - + 2HCl + (aq) Mg (s) MgCl2 + H2 (aq) (g) hydrogen peroxide magnesium chloride + hydrogen Reactants Products balanced? Cl 1 2 2 Mg 1 1 H 1 2 2
  49. 49. Types of Reactions A+B AB AB A+B replacement replacement double single AB + C CB + A AB + CD AD + BC heat H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2O
  50. 50. Double Replacement Reactions These can be simplified as AB + CD  AD + CB Where the anions and cations of two compounds trade places. + - + + - + - + + - KI + Pb(NO3)2 KNO3 + PbI2 (aq) (aq) (aq) (s)potassium iodide + lead nitrate potassium nitrate + lead iodide Reactants Products balanced? K I Pb NO3 Nitrate is a polyatomic ion and must be kept together
  51. 51. Double Replacement Reactions These can be simplified as AB + CD  AD + CB Where the anions and cations of two compounds trade places. + - + + - + - + + - KI + Pb(NO3)2 KNO3 + PbI2 (aq) (aq) (aq) (s)potassium iodide + lead nitrate potassium nitrate + lead iodide Reactants Products balanced? K 1 1 I 1 2 Pb 1 1 NO3 2 1 Nitrate is a polyatomic ion and must be kept together
  52. 52. Double Replacement Reactions These can be simplified as AB + CD  AD + CB Where the anions and cations of two compounds trade places. + - + + - + - + + - KI (aq) + Pb(NO3)2 2KNO3 + PbI2 (aq) (aq) (s)potassium iodide + lead nitrate potassium nitrate + lead iodide Reactants Products balanced? K 1 1 2 I 1 2 Pb 1 1 NO3 2 1 2 Nitrate is a polyatomic ion and must be kept together
  53. 53. Double Replacement Reactions These can be simplified as AB + CD  AD + CB Where the anions and cations of two compounds trade places. + - + + - + - + + - 2KI + (aq) Pb(NO3)2 2KNO3 + PbI2 (aq) (aq) (s)potassium iodide + lead nitrate potassium nitrate + lead iodide Reactants Products balanced? K 1 2 1 2 I 1 2 2 Pb 1 1 NO3 2 1 2 Nitrate is a polyatomic ion and must be kept together
  54. 54. Let’s look at that again… KI + Pb(NO3)2 KNO3 + PbI2 (aq) (aq) (aq) (s)potassium iodide + lead nitrate potassium nitrate + lead iodideWhich ions form? + K K 2+Pb Pb - I I And the polyatomic ion - NO3
  55. 55. Let’s look at that again… KI + Pb(NO3)2 KNO3 + PbI2 (aq) (aq) (aq) (s)potassium iodide + lead nitrate potassium nitrate + lead iodide + - + - -K I - K NO3 I 2+ NO3 2+ Pb - Pb -The 2+ lead cationneeds to be balanced NO3 Iby two single anions. The total number of atoms on each side are not balanced. Reactants Products K 1 1 I 1 2 Pb 1 1 NO3 2 1
  56. 56. Let’s look at that again… 2KI + Pb(NO3)2 (aq) 2KNO3 + PbI2 (aq) (aq) (s)potassium iodide + lead nitrate potassium nitrate + lead iodide + - + - -K I - K NO3 I 2+ NO3 2+ + - Pb - + - Pb -K I NO3 K NO3 I Now they are. Reactants Products K 1 2 1 2 I 1 2 2 Pb 1 1 NO3 2 1 2
  57. 57. Types of Reactions A+B AB AB A+B replacement replacement double single AB + C CB + A AB + CD AD + BC heat H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2O
  58. 58. Neutralisation Reactions These can be simplified as HA + BOH  H20 + BA Where the acid (HA) is neutralized by the base (BOH), giving water and a salt (AB). H[A] + [B]OH(aq) (aq) [B][A] + H2O (g) (g) acid + base salt + water These brackets don’t get used in equations – they are just there to show what is happening e.g HCl + NaOH(aq) (aq) NaCl + H2O (aq) (g)hydrochloric acid + sodium hydroxide sodium chloride + water Reactants Products Cl Na O H
  59. 59. Neutralisation Reactions These can be simplified as HA + BOH  H20 + AB Where the acid (HA) is neutralized by the base (BOH), giving water and a salt (BA). H[A] + [B]OH(aq) (aq) [B][A] + H2O (g) (g) acid + base salt + water These brackets don’t get used in equations – they are just there to show what is happening e.g HCl + NaOH(aq) (aq) NaCl + H2O (aq) (g)hydrochloric acid + sodium hydroxide sodium chloride + water Reactants Products Cl 1 1 Na 1 1 O 1 1 H 2 2
  60. 60. Types of Reactions A+B AB AB A+B replacement replacement double single AB + C CB + A AB + CD AD + BC heat H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2O
  61. 61. Balancing Equation Practice Now try the activities on this PhET simulation to help practice balancing equations. 1. Complete the introduction stage. 2. Some of the examples are on the sheet. 3. Try the challenge quizzes. http://phet.colorado.edu/en/simulation/balan cing-chemical-equations
  62. 62. Classify and balance these… Cell respiration? C6H12O6 (s) + O2 (g) heat CO2 + H2O (g) (g) glucose + oxygen carbon dioxide + water
  63. 63. Housekeeping classToday we need to make sure everyone is up to date on all work and canunderstand balancing and reactions. 1. Check all One World work has been submitted. 2. Check in with incomplete elements task people. 3. Work through last week’s reactions and balance them. 4. Turn these sheets back in to be checked again. If you have completed everything and are all up to date you can: • practice balancing and naming using the resources on the GoogleSite • Find out more about the ‘Mole’ and stoichiometry MrT’s promise: • All Chem work will be checked and graded by Thursday • If you performed poorly in One World you can do another essay or article in your own time. Due 16 Jan at the very latest.
  64. 64. For more resources. Please consider a donation to charity via Biology4Good. Click here for more information about Biology4Good charity donations.This is a Creative Commons presentation. It may be linked and embedded but not sold or re-hosted.

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