Unit 2: Chemical Reactions Unit Review Answer Key

SCH 3U Unit 2: Chemical Reactions Unit Review Answer Key Page 117 1. Requirements for combustion are fuel, oxygen and some heat to start the reaction. All combustion reactions produce more heat than they need to get started. Complete combustion occurs when a metal or a non-metal burns in oxygen to produce its oxide or if a hydrocarbon fuel burns in oxygen

to produce only CO2(g) and H2O(g). Incomplete combustion occurs when a hydrocarbon fuel burns

in oxygen to likely still produce CO2(g) and H2O(g) but also produce CO(g) and/or C(s) (soot). Carbon monoxide is a toxic gas that can displace oxygen in body tissue and cause death. Page 121

5a) 2Al(s) + 3F2(g)  2AlF3(s) synthesis b) 2KCl(s)  2K(s) + Cl2(g) decompositions

c) S8(s) + 4O2(g)  8SO2(g) syntheis d) CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) complete comb.

e) 2Al2O3(s)  4Al(s) + 3O2(g) decomposition f) 2Hg(l) + O2(g)  2HgO(s) synthesis and also combustion 6a) Reactants will be two or more smaller bits of matter (e.g. elements or small compounds) that will come together to produce a single product. b) Only one reactant will be present. It will be broken up into smaller bits of matter to the right of the arrow. c) There are generally two reactants. Oxygen must be one of the reactants. The other reactant is most often a hydrocarbon fuel or an element.

7a) 2Na(s) + Cl2(g)  2NaCl(s) synthesis b) 2CuO(s)  2Cu(l) + O2(g) decomposition

c) Cu(s) + Cl2(aq)  CuCl2(s) synthesis

Page 123 2a) i) Butane is likely to take part in either complete or incomplete combustion as it is a hydrocarbon fuel. ii) Calcium carbonate could take part in a decomposition reaction to produce carbon dioxide gas. It could also take part in a single or a double displacement reaction. iii) Together, Li and Br could take place in a synthesis reaction to produce LiBr(s). iv) Copper(II) sulphate pentahydrate is likely to take place in a decomposition reaction to release the water molecules (see top of page 120).

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7 and 8a) KOH(aq) + HNO3(aq)  KNO3(aq) + H2O(l) This double displacement reaction (acid-base neutralization) is one reaction (of many) that would produce potassium nitrate. According to the solubility table on page 137, potassium nitrate will form a solution rather than a precipitate in water.)

b and c) This reaction will work for both b) and c) MgCl2(aq) + Ca(OH)2 CaCl2(aq) + Mg(OH)2(s)

d) 2AlCl3(aq) + 3Cu2SO4(aq)  Al2(SO4)3(aq) + 6CuCl(s)

e) 2KI(aq) + Pb(NO3)2(aq)  PbI2(s) + 2KNO3(aq)

f) 3Ca(NO3)2(aq) + 2K3PO4(aq)  Ca3(PO4)2(s) + 6KNO3(aq)

g) 2NH4OH(aq) + H2CO3(aq)  (NH4)2CO3(aq) + 2H2O(aq)

10a) Cl2(g) + 2NaBr(aq)  Br2(g) + 2NaCl(aq) single displacement

b) H2SO4(aq) + NaOH(aq)  H2O(l) + Na2SO4(aq) double displacement (acid-base neutralization)

c) 3Ca(NO3)2 (aq) + 2Na3PO4(aq)  Ca3(PO4)2(s) + 6NaNO3(aq) double displacement

11a) Al(s) + 3AgNO3(aq) 3Ag(s) + Al(NO3)3(aq) b) Cl2(g) + 2NaBr(aq)  Br2(g) + 2NaCl(aq)

c) Zn(s) + 2HCl(aq)  H2(g) + ZnCl2(aq) d) 2AgNO3(aq) + MgCl2(aq)  2AgCl(s) + Mg(NO3)2(aq)

e) Na2C2O4(aq) + CaCl2(aq)  CaC2O4(s) + 2NaCl(aq) f) 2Na(s) + 2H2O(l)  H2(g) + 2NaOH(aq) 3+ g) 3KOH(aq) + FeCl3(aq)  3KCl(aq) + Fe(OH)3(s) (Fe is the most common ion of Fe – see periodic table.) Page 146 [PLEASE NOTE: ALL QUESTIONS THE TEST STUDY GUIDE SAYS ARE ON PAGE 346 ARE ON PAGE 146!!!]

3a) S8(s) + 4O2(g)  8SO2(g) synthesis and combustion e) balance with 2-1-2-1 single displ b) already balanced double displacement (acid-base neutralization) f) balance with 1-2-2-1 double displ c) balance with the coefficients: 1-3-2 synthesis reaction g) balance with 1-5-1 synthesis d) balance with: 1-1-2 decomposition reaction h) balance with 1-2-1-1 single displ 4a) word equation: potassium chlorate(s)  potassium chloride(s) + oxygen(g)

skeleton equation: KClO3(s)  KCl(s) + O2(g) balanced chemical equation: 2KClO3(s)  2KCl(s) +3O2(g) b) word equation: sodium(s) + water(l)  hydrogen(g) + sodium hydroxide(aq)

skeleton equation: Na(s) + H2O(l)  H2(g) + NaOH(aq)

balanced chem equation: 2Na(s) + 2H2O(l)  H2(g) + 2NaOH(aq) c) word equation: carbon(s) + oxygen(g)  carbon dioxide(g) skeleton equation: C(s) + O2(g)  CO2(g)

balanced chem. equation: C(s) + O2(g)  CO2(g) d) word equation: zinc(s) + sulphuric acid(aq)  hydrogen(g) + zinc sulphate(aq)

skeleton equation: Zn(s) + H2SO4(aq)  H2(g) + ZnSO4(aq)

balanced chem. equation: Zn(s) + H2SO4(aq)  H2(g) + ZnSO4(aq) e) word equation: silver nitrate(aq) + potassium iodide(aq)  silver iodide(s) + potassium nitrate(aq) [Use the solubility table, pg. 137, to determine which product is the precipitate.]

skeleton equation: AgNO3(aq) + KI(aq)  AgI(s) + KNO3(aq)

balanced chem. equation: AgNO3(aq) + KI(aq)  AgI(s) + KNO3(aq) f) word equation: sodium sulphate(aq) + barium chloride(aq)  barium sulphate(s) + sodium chloride(aq)

skeleton equation: Na2SO4(aq) + BaCl2(aq)  BaSO4(s) + NaCl(aq)

balanced chem. equation: Na2SO4(aq) + BaCl2(aq)  BaSO4(s) + 2NaCl(aq) g) word equation: iron(s) + oxygen(g)  iron(III) oxide(s)

skeleton equation: Fe(s) + O2(g)  Fe2O3(s) balanced chem. equation: 4Fe(s) + 3O2(g)  2Fe2O3(s) h) word equation: sulphur trioxide(g) + water(g)  sulphuric acid(aq)

skeleton equation: SO3(g) + H2O(g)  H2SO4(aq)

balanced chem. equation: SO3(g) + H2O(g)  H2SO4(aq) 5. Precipitates: c, h, i, j 6c) calcium nitrate(aq) + sodium sulphate(aq)  calcium sulphate(s) + sodium nitrate(aq) h) silver nitrate(aq) + sodium iodide(aq)  silver iodide(s) + potassium nitrate(aq) i) copper nitrate(aq) + sodium chloride(aq)  copper(I) chloride(s) + sodium chloride(aq) j) lead(II) nitrate(aq) + potassium sulphate(aq)  lead(II) sulphate(s) + potassium nitrate(aq)

8a) Li(s) + 2H2O(l)  H2(g) + 2LiOH(aq) single displacement

b) K(s) + 2H2O(l)  H2(g) + 2KOH(aq) single displacement

c) Cu(s) + AgNO3(aq)  Ag(s) + CuNO3(aq) single displacement – Cu is more reactive than Ag

d) no reaction e) no reaction f) 2Al(s) + 6HCl(aq)  3H2(g) + 2AgCl3(aq) single displacement

g) Pb(s) + Cu(NO3)2(aq)  Cu(s) + Pb(NO3)2(aq) h) no reaction 9a) A single displacement reaction between the halogens chlorine and iodine has occurred. b) products will be: iodine and potassium chloride(aq)

c) Cl2(g) + 2KI(aq)  I2 + 2KCl(aq) d) Chlorine is a smaller molecule than iodine, has more effective nuclear charge, is more reactive. So, the chlorine readily reacts with the KI(aq) and displaces the iodine. 10a) nitrogen, bromine, fluorine (least  most reactive) The smaller the non-metal atom, the more reactive the non-metal. Smaller atoms have more effective nuclear charge and so more “pull” of valence electrons toward the nucleus. Because they are seeking more electrons to complete their valence shell, this makes the smallest atom (fluorine) the most reactive. b) rubidium, potassium, magnesium (least  most reactive) The larger a metal atom, the more reactive the element. This is because metals are in the business of losing one or more electrons to get a full valence shell. The larger the atom, the less the effective nuclear charge felt by the outermost electrons, so the easier it is to lose and electron – thus the more reactive the element.

Page 520 43 2. C14H30(l) + O2(g)  14CO2(g) + 15H2O(g) or 2C14H30(l) + 43O2(g)  28CO2(g) + 30H2O(g) 2

Page 527 14. In complete combustion of a hydrocarbon fuel, the only products are carbon dioxide gas and water vapour. When incomplete combustion occurs, less carbon dioxide gas is produced and carbon monoxide and/or soot (solid carbon) are produced.