1. 1.3 Chemical Equations

2. Teacher Notes These lessons assume students have already studied ‘Bonding’ and hence have an understanding of charges of ions. Also an understanding of elements that exist as diatomic molecules (e.g oxygen, nitrogen etc)

3. Starter What give me the symbols for the following ions and their charges

4. Assessment Objectives 1.3.1 Deduce chemical equations when all the reactants and products are given. 1.3.2 Identify the mole ratio of any two species in a chemical equation. (Balancing) 1.3.3 Apply the state symbols (s), (l), (g), and (aq).

5. Assessment Objective 1.3.1 Deduce chemical equations when all the reactants and products are given. 1.3.3 Apply the state symbols (s), (l), (g), and (aq).

6. Start Memorising Common Names for Some Compounds Sulfuric acid H2SO4 Nitric acid HNO3 Ammonia NH3 Hydrochloric acid HCl Ethanoic acid CH3COOH Carbon monoxide CO Sulfur dioxide SO2

7. Start Learning Names For Polyatomic Ions Sulphate SO4 2- Nitrate NO3 - Phosphate PO4 3- Carbonate CO3 2- Hydroxide OH - Hydrogen Carbonate HCO3 - Permanganate MnO4 - Making Flash Cards in workbook

8. Chemical Equations Can be expressed in three methods: Word equations Iron + chorine  iron (III) chloride Skeletal equations Fe + Cl2  FeCl3 Balanced equations 2Fe + 3Cl2  2FeCl3 (by adding coefficients, not subscripts)

9. Writing Word Equations Zinc and lead (II) nitrate react to form zinc nitrate and lead. Zinc + Lead (II) nitrate  Zinc nitrate + Lead ‘React to Give’‘Plus’ or ‘And’ Practice these in your workbook

10. Writing Symbol Equations Mole Ratio: Ratio of moles of one compound to another, the coefficients provide this State symbols 2Fe(s) + 3Cl 2 (g)  2FeCl 3 (s) Thermodynamic data 2Fe + 3Cl 2  2FeCl 3 ΔH o = -750 kJ mol -1 Keep in simplest form: 4H 2 (g) + 2O 2 (g)  4H 2 O(l) vs… 2H 2 (g) + O 2 (g)  2H 2 O(l)

11. Law of Conservation of Matter In a chemical (non-nuclear) reaction, atoms are neither created nor destroyed. For an equation to be balanced the number of atoms of each element is the same on both sides of the equation. H 2 (g) + O 2 (g)  H 2 O (l)(unbalanced) 2H 2 (g) + O 2 (g)  2H 2 O (l)(balanced) K(s) + H 2 0(l)  KOH (aq) + H 2 (g)(unbalanced) 2K(s) + 2H 2 0(l)  2KOH (aq) + H 2 (g)(balanced) C 6 H 12 O 6 + O 2  CO 2 + H 2 O(unbalanced) C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O(balanced)

12. 1.3.1 Deduce chemical equations when all the reactants and products are given. Aluminum bromide + chlorine yield aluminum chloride + bromine 2AlBr 3 + 3Cl 2  2AlCl 3 + 3Br 2 Seven elements are diatomic: H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 Copper + oxygen produces copper(I) oxide 4Cu + O 2  2Cu 2 O

13. Practice These Sodium chlorate decomposes to sodium chloride and oxygen gas Aluminum nitrate plus sodium hydroxide yields aluminum hydroxide plus sodium nitrate Ethane (C 2 H 6 ) burns in oxygen to produce carbon dioxide and water vapor

14. Answers Sodium chlorate decomposes to sodium chloride and oxygen gas 2NaClO 3  2NaCl + 3O 2 Aluminum nitrate plus sodium hydroxide yields aluminum hydroxide plus sodium nitrate Al(NO 3 ) 3 + 3NaOH  Al(OH) 3 + 3NaNO 3 Ethane (C 2 H 6 ) burns in oxygen to produce carbon dioxide and water vapor 2C 2 H 6 + 7O 2  4CO 2 + 6H 2 O

15. Other Symbols used in chemical reactions + Used to separate two reactants or products A “Yields” arrow (  ) separates products from reactants  Used in place of  for reversible reactions (s) Designates a solid reactant or product (l) Designates a liquid reactant or product (g) Designates a gaseous reactant or product (aq) Designates an aqueous reactant or product  Indicates that heat is supplied to the reaction

16. Rules for Balancing Equations 1)Write the correct formulas for the reactants on the left side of the yield sign and products on the right side. 2)Count the number of atoms of each element in the products and the reactants. 3)Balance the elements one at a time by using coefficients. Do not change the subscripts in the chemical formulas. 4)Check each atom or polyatomic ion to make sure the equation is balanced. 5)Make sure all coefficients are in the lowest possible ratio.

17. Tricks This is a case of trial and error, it made take a few tries to get it right. Start with elements that occur in one compound on each side. Treat polyatomic ions that repeat as if they were a single entity When adding coefficients, start by doubling an element that is present in an odd number.

18. Rules for Balancing Equations 1)Write the correct formulas for the reactants on the left side of the yield sign and products on the right side. 2)Count the number of atoms of each element in the products and the reactants. 3)Balance the elements one at a time by using coefficients. Do not change the subscripts in the chemical formulas. 4)Check each atom or polyatomic ion to make sure the equation is balanced. 5)Make sure all coefficients are in the lowest possible ratio N 2 + H 2  NH 3 Reactants Products 2N 2H  1N 3H Balance N by putting 2 in front of NH 3 N 2 + H 2  2NH 3 Balance H by putting 3 in front of H 2 N 2 + 3H 2  2NH 3 2N 6H  2N 6H Lowest ratio of coefficients N 2 + 3H 2  2NH 3

19. Rules for Balancing Equations 1)Write the correct formulas for the reactants on the left side of the yield sign and products on the right side. 2)Count the number of atoms of each element in the products and the reactants. 3)Balance the elements one at a time by using coefficients. Do not change the subscripts in the chemical formulas. 4)Check each atom or polyatomic ion to make sure the equation is balanced. 5)Make sure all coefficients are in the lowest possible ratio. KClO 3  KCl + O 2 Reactants Products 1K 1Cl 3O  1K 1Cl 2O Balance O by putting 2 in front of KClO 3 and 3 in front of O 2 2KClO 3  KCl + 3O 2 Balance K & Cl by putting 2 in front of KCl 2KClO 3  2KCl + 3O 2 2K 2Cl 6O  2K 2Cl 6O Lowest ratio of coefficients 2KClO 3  2KCl + 3O 2

20. Balance These…… a)Mg + HCl → MgCl2+ H2 b)Ca + N2 → Ca3N2 c)NH4NO3 → N2O + H2O d)BiCl3+ H2S → Bi2S3+ HCl e)C4H10+ O2 → CO2+ H2O f)O2+ C6H12O6 → CO2+ H2O g)NO2+ H2O → HNO3+ NO h)Cr2(SO4)3+ NaOH → Cr(OH)3+ Na2SO4 i)Al4C3+ H2O → CH4+ Al(OH)3

21. Assessment Objectives 1.3.2 Identify the mole ratio of any two species in a chemical equation. (Balancing)

22. Mole Ratio Coefficients are in particles or in moles 2 molecules NaClO 3  2 molecules NaCl + 3 molecules O 2 2 mol NaClO 3  2 mol NaCl + 3 mol O 2 We will use moles because we measure moles in grams The coefficients give us mole ratios Mole ratio NaClO 3 :NaCl is 2:2 Mole ratio NaCl:O 2 is 2:3 Mole ratio O 2 :NaCl is 3:2

23. Mole Ratio Consider the following equation 2K 2 Cr 2 O 7 + 2H 2 O + 3S  4KOH + 2Cr 2 O 3 + 3SO 2 What is the KOH:S mole ratio? What is the K 2 Cr 2 O 7 :Cr 2 O 3 mole ratio? What is the mole ratio between sulfur dioxide and water? What species will give mole ratios of 4:2?

24. Mole Ratio Consider the following equation 2K 2 Cr 2 O 7 + 2H 2 O + 3S  4KOH + 2Cr 2 O 3 + 3SO 2 What is the KOH:S mole ratio? What is the K 2 Cr 2 O 7 :Cr 2 O 3 What is the mole ratio between sulfur dioxide and water? What species will give mole ratios of 4:2? 4:3 2:2 3:2 KOH:K 2 Cr 2 O 7 KOH:H 2 OKOH:Cr 2 O 3

25. Looking at a reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe) Be sure you have a balanced reaction before you start! Example: 2 Na + Cl 2  2 NaCl This reaction tells us that by mixing 2 moles of sodium with 1 mole of chlorine we will get 2 moles of sodium chloride What if we wanted 4 moles of NaCl? 10 moles? 50 moles?

26. Mole Ratio These mole ratios can be used to calculate the moles of one chemical from the given amount of a different chemical Example: How many moles of chlorine is needed to react with 5 moles of sodium (without any sodium left over)? 2 Na + Cl 2  2 NaCl = 2.5 moles Cl 2

27. How many moles of sodium chloride will be produced if you react 2.6 moles of chlorine gas with an excess (more than you need) of sodium metal? 2 Na + Cl 2  2 NaCl 5.2 moles NaCl

28. 1.3.2 Practice Write the balanced reaction for hydrogen gas reacting with oxygen gas. 2 H 2 + O 2  2 H 2 O How many moles of reactants are needed? What if we wanted 4 moles of water? What if we had 3 moles of oxygen, how much hydrogen would we need to react and how much water would we get? What if we had 50 moles of hydrogen, how much oxygen would we need and how much water produced? 2 mol H 2 1 mol O 2 4 mol H 2 2 mol O 2 6 mol H 2, 6 mol H 2 O 25 mol O 2, 50 mol H 2 O

29. Different Types of Chemical Reactions There are six types of chemical reactions we will talk about: 1. Synthesis reactions 2. Decomposition reactions 3. Single displacement reactions 4. Double displacement reactions 5. Combustion reactions 6. Neutralisation Reaction You need to be able to identify the type of reaction and predict the product(s)

30. Identify types of chemical reactions 1) Synthesis or Combination Reaction: Two or more substances combine to form a single substance. A + B → AB 2Na(s) + Cl 2 (g)  2NaCl(s) CaO(s) + H 2 O(l)  Ca(OH) 2 (aq) 2H 2 (g) + O 2 (g)  2H 2 O (l) 4Fe(s) + 3O 2 (g)  2Fe 2 O 3 (s) N 2 (g) + 3H 2 (g)  2NH 3 (g)

31. Practice Predict the products. Write and balance the following synthesis reaction equations. Sodium metal reacts with chlorine gas Na (s) + Cl 2(g)  Solid Magnesium reacts with fluorine gas Mg (s) + F 2(g)  Aluminum metal reacts with fluorine gas Al (s ) + F 2(g)  22NaCl (s) MgF 2(s) AlF 3(s) 2 3 2

32. Identify types of chemical reactions 2) Decomposition Reactions: A single substance is broken down into two or more substances. AB → A + B CaCO 3 (s)  CaO(s) + CO 2 (g) 2H 2 O(l)  2H 2 (g) + O 2 (g) 2H 2 O 2 (aq)  2H 2 O(l) + O 2 (g)

33. Practice Predict the products. Then, write and balance the following decomposition reaction equations: Solid Lead (IV) oxide decomposes PbO 2(s)  Aluminum nitride decomposes AlN (s)  2 Pb (s) + O 2(g) Al (s) + N 2(g) 2

34. Practice Identify the type of reaction for each of the following synthesis or decomposition reactions, and write the balanced equation: N 2(g) + O 2(g)  BaCO 3(s)  Co (s) + S (s)  NH 3(g) + H 2 CO 3(aq)  NI 3(s)  Synthesis Decomposition Synthesis Decomposition 2 NO (g) (NH 4 ) 2 CO 3(s) N 2 (g) + I 2 (s) Co 2 S 3 (s) BaO (s) + CO 2 (g) (make Co be +3) 23 2 3 2

35. Identify types of chemical reactions Types of Chemical Reactions 3) Single-Replacement Reactions: One element replaces another in a compound. Mg(s) + Zn(NO 3 ) 2 (aq)  Mg(NO 3 ) 2 (aq) + Zn(s) 2K(s) + 2H 2 O(l)  2KOH (aq) + H 2 (g) Cu(s) + 2AgNO 3 (aq)  Cu(NO 3 ) 2 (aq) + 2Ag(s) 2Al(s) + Fe 2 O 3 (s)  Al 2 O 3 (s) + 2Fe(s) Cl 2 (g) + 2NaBr(aq)  2NaCl(aq) + Br 2 (g)

36. Single Replacement Reactions Write and balance the following single replacement reaction equation: Zinc metal reacts with aqueous hydrochloric acid Zn (s) + HCl (aq)  ZnCl 2 + H 2(g) Note: Zinc replaces the hydrogen ion in the reaction 2

37. Identify types of chemical reactions Types of Chemical Reactions 4) Double-Replacement Reactions: Ions of two reacting compounds trade places. Na 2 CO 3 (aq) + CaCl 2 (aq)  CaCO 3 (s) + 2NaCl(aq) Na 2 S(aq) + Cd(NO 3 ) 2 (aq)  CdS(s) + 2NaNO 3 (aq) NaOH(aq) + HCl(aq)  NaCl(aq) + H 2 O(l) H 2 SO 4 (aq) + 2NaCN(aq)  Na 2 SO 4 (aq) + 2HCN(g)

38. Practice Predict the products. Balance the equation 1. HCl (aq) + AgNO 3(aq)  2. CaCl 2(aq) + Na 3 PO 4(aq)  3. Pb(NO 3 ) 2(aq) + BaCl 2(aq)  4. FeCl 3(aq) + NaOH (aq)  5. H 2 SO 4(aq) + NaOH (aq)  6. KOH (aq) + CuSO 4(aq)  HNO 3(aq) + AgCl (s) Ca 3 (PO 4 ) 2(s) + NaCl (aq) 326 PbCl 2(s) + Ba(NO 3 ) 2(aq) Fe(OH) 3(s) + NaCl (aq) 33 H 2 O (l) + Na 2 SO 4(aq) 22 K 2 SO 4(aq) + Cu(OH) 2(s) 2

39. Identify types of chemical reactions Types of Chemical Reactions 5) Combustion Reactions: A compound reacts with oxygen. Products are usually carbon dioxide and water. CH 4 (g) + O 2 (g)  CO 2 (g) + H 2 O(g) C 3 H 8 (g) + 5O 2 (g)  3CO 2 (g) + 4H 2 O(g) 2C 8 H 18 (l) + 25O 2 (g)  16CO 2 (g) + 18H 2 O(g) C 2 H 5 OH(l) + 3O 2 (g)  2CO 2 (g) + 3H 2 O(g)

40. 5. Combustion Reactions Combustion reactions occur when a hydrocarbon reacts with oxygen gas. This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”: 1) A Fuel (hydrocarbon) 2) Oxygen to burn it with 3) Something to ignite the reaction (spark)

41. A Summary of the Chemical Reaction Types S: A + B → AB D: AB → A + B SR: A + BC → AC + B DR: AB + CD → AD + CB C: C X H Y + O 2 → CO 2 + H 2 O

42. Combustion Example C 5 H 12 + O 2  CO 2 + H 2 O Write the products and balance the following combustion reaction: C 10 H 22 + O 2  5 68 CO 2 + H 2 O

43. Mixed Practice State the type, predict the products, and balance the following reactions: 1. BaCl 2 + H 2 SO 4  2. C 6 H 12 + O 2  3. Zn + CuSO 4  4. Cs + Br 2  5. FeCO 3  BaSO 4 + HCl2 CO 2 + H 2 O669 ZnSO 4 + Cu CsBr2 2 FeO + CO 2

44. Returning to Reaction Types Have looked at several types of reactions without worrying about balancing. However, all equations should be balanced. Predict the products and balance these:(recall, metals above replace metals below, reactions with water yield metal hydroxides) Fe + CuSO4 → Ni+ NaCl → Al+ CuCl2 → Li+ ZnCO3 → Li + H2O → Al+O2 →