CHEMISTRY WKST CH. 7 & 8 REVIEW (REACTIONS & EQUATIONS) NAME: JMS 1) What are the 5 evidences that a chemical reaction took place? precipitate forms color change gas released temperature change 2) Consider the equation: 4Al(s) + 3O2(g) 2Al2O3(s) a) Name the reactants. aluminum (Al), oxygen gas (O2) b) Name the product. aluminum oxide c) Is the equation balanced? yes d) What is the physical state of Al2O3? solid e) What does the mean? yields 3) Change these word equations to balanced equations using symbols. energy released a) On heating, solid calcium carbonate yields solid calcium oxide and gaseous carbon dioxide. CaCO3(s) CaO(s) + CO2(g) b) Solid lithium metal reacts with oxygen gas to form solid lithium oxide. 4Li(s) + O2(g) 2Li2O(s) c) Solid zinc metal reacts with aqueous hydrochloric acid to form aqueous zinc chloride and hydrogen gas. Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g) 4) What law requires us to balance chemical equations? Law of Conservation of Matter 5) When balancing chemical equations, what is the only thing you are allowed to change? The coefficients in front of the formulas of the substances in the equation. 6) Balance the following equations. a) 3Fe + 4H2O Fe3O4 + 4H2 b) 2AlBr3 + 3Cl2 2AlCl3 + 3Br2 c) 2HNO3 + Ba(OH)2 Ba(NO3)2 + 2H2O d) C8H16 + 12O2 8CO2 + 8H2O e) Na2CO3 + 2HCl 2NaCl + H2O + CO2 f) 3K2CO3 + 2Al(ClO4)3 Al2(CO3)3 + 6KClO4 g) 4H2O + Cr + Na2CrO4 2Cr(OH)3 + 2NaOH 7) What are the 4 main driving forces in making a reaction occur? forming a precipitate forming molecular substances like water forming a gas transferring electrons (redox)
8) What does the triangle above the arrow mean in a chemical equation? -2- the reactants are being heated 9) Classify each of the following statements as describing a double replacement, single replacement, combustion, synthesis, decomposition or acid-base. There may be more than one answer for a statement give them all. a) O2(g) is always a reactant. combustion b) Reaction is always endothermic. decomposition c) 2 compounds reacting to form 2 products, one which is an insoluble solid, gas or water. double replacement d) Reaction is always exothermic. combustion, synthesis e) Forms one product. synthesis f) Forms water and a salt. acid-base g) An element and a compound react to form 2 products, 1 an element and the other a compound. single repl. h) Has only one reactant. decomposition 10) When burning a hydrocarbon, what are the products? CO2(g), H2O(l) 11) Classify each of the following reactions as double replacement, single replacement, combustion, synthesis, decomposition or acid-base. Include all possibilities. a) Cu + Cl2 CuCl2 synthesis b) KBr + AgNO3 AgBr + KNO3 double replacement c) 2Ba + O2 2BaO synthesis, combustion d) Fe + CuSO4 FeSO4 + Cu single replacement e) C3H8 + 5O2 3CO2 + 4H2O combustion f) HCl + KOH KCl + H2O acid-base / double replacement g) 2KClO3 2KCl + 3O2 decomposition 12) Tell what physical state the following would be in water. a) K2SO4 (aq) d) MgO (s) b) NH4OH (aq) e) Cu(NO3)2 (aq) c) BaCO3 (s) f) AlPO4 (s) 13) List the 7 diatomic elements and their physical state at room temperature. H2(g), N2(g), O2(g), F2(g), Cl2(g), Br2(l), I2(s) 14) When we did the single replacement lab the only reactions we did with Ca was with an acid and with H2O. Why did we not do the other reactions with Ca and the solutions? Calcium reacts with H2O. Since the other solutions were in H2O, the Ca will react with the H2O as well as the solute. In other words, the Ca + H2O reaction will interfere with the desired reactions.
15) Why does Zn react more vigorously with an acid than Sn? Zn is much more reactive with an acid than Sn as shown by Zn being farther away from the acid on the activity series than Sn is. 16) For each of the following molecular equations, write the ionic equation, circle the spectator ions (if any), and write the net ionic equation. a) Zn(NO3)2(aq) + K2CO3(aq) ZnCO3(s) + 2KNO3(aq) Zn 2+ (aq) + 2NO3 (aq) + 2K + (aq) + CO3 2 (aq) ZnCO3(s) + 2K + (aq) + 2NO3 (aq) Zn 2+ (aq) + CO3 2 (aq) ZnCO3(s) b) Mg(s) + 2AgNO3(aq) Mg(NO3)2(aq) + 2Ag(s) Mg(s) + 2Ag + (aq) + 2NO3 (aq) Mg 2+ (aq) + 2NO3 (aq) + 2Ag(s) Mg(s) + 2Ag + (aq) Mg 2+ (aq) + 2Ag(s) c) HClO4(aq) + LiOH(aq) H2O(l) + LiClO4(aq) H + (aq) + ClO4 (aq) + Li + (aq) + OH (aq) H2O(l) + Li + (aq) + ClO4 (aq) H + (aq) + OH (aq) H2O(l) 17) Why do we sometimes get a precipitate when mixing 2 solutions? Sometimes there are 2 ions in the resulting mixture that when they come in contact with each other will form an insoluble solid. 18) If a solution of KCl and NaCl is mixed with another solution containing MgCl2, how many different kinds of ions are present? Would there be a precipitate? Why or why not? There are 4 different ions present. No there will not be a precipitate since the chlorides of the cations (the positive ions) are soluble. Also, since Cl is the anion in all 3 solutions, no new substances would be formed. 19) a) H 1+ b) OH 1 20) a) strong acid e) weak base h) weak acid b) weak acid f) strong base i) strong base c) strong acid g) weak acid j) weak base d) strong acid 21) Strong acids completely dissociate in water while weak acids only partially dissociate in water. 22) a) HBr(aq) H 1+ (aq) + Br 1 (aq) b) HF(aq) H 1+ (aq) + F 1 (aq) c) NaOH(aq) Na 1+ (aq) + OH 1 (aq) d) Ca(OH)2(aq) Ca 2+ (aq) + 2OH 1 (aq) e) H2CrO4(aq) H 1+ (aq) + HCrO4 1 (aq) HCrO4 1 (aq) H 1+ (aq) + CrO4 2 (aq)
23) H 1+ (aq) + OH 1 (aq) H2O 24) Predict the products for the following equations. Include physical states for the products. If no reaction, write NR and tell why. a) C6H6(l) + O2(g) CO2(g) + H2O(l) b) Cu(s) + AgNO3(aq) Cu(NO3)2(aq) + Ag(s) or CuNO3(aq) + Ag(s) c) Pb(ClO3)2(aq) + K2SO4(aq) PbSO4(s) + KClO3(aq) d) CuO(s) Cu(s) + O2(g) e) MgCO3(s) + H2SO4(aq) MgSO4(aq) + CO2(g) + H2O(l) f) NH4OH(aq) + H3PO4(aq) H2O(l) + (NH4)3PO4(aq) g) SO3(g) + H2O(l) H2SO4(aq) h) Na2S(aq) + Ni(NO3)2(aq) NaNO3(aq) + NiS(s) i) Ba(ClO3)2(s) BaCl2(s) + O2(g) j) Zn(s) + CuCl2(aq) ZnCl2(aq) + Cu(s) k) AlCl3(aq) + Pb(NO3)2(aq) Al(NO3)3(aq) + PbCl2(s) l) Rb2O(s) + H2O(l) RbOH(aq) m) CaO(s) + CO2(g) CaCO3(s) n) Cu(s) + Li2CO3(aq) NR Cu is less reactive than Li and therefore cannot replace it. o) HgO(l) Hg(l) + O2(g) p) K(s) + Cl2(g) KCl(s) q) Cl2(g) + KBr(aq) KCl(aq) + Br2(l) r) H2SO3(g) H2O(l) + SO2(g) s) LiOH(aq) + HBr(aq) LiBr(aq) + H2O(l) t) BaCO3(s) BaO(s) + CO2(g) u) K(s) + H2O(l) KOH(aq) + H2(g) v) BaCl2(s) + O2(g) Ba(ClO3)2(s) w) RbOH(s) Rb2O(aq) + H2O(l) x) H2SO4(aq) + KOH(aq) H2O(l) + K2SO4(aq)
VOCAB TO KNOW: endothermic: process that absorbs energy (heat) exothermic: process that gives off energy (heat) hydrocarbon: compound made up of carbon and hydrogen insoluble: won t dissolve oxidation: process that loses electrons precipitate: solid formed by the reaction between two solutions products: substances formed in a reaction they will be on the right side of the arrow in a chemical equation reactants: substances that begin a reaction they will be on the left side of the arrow in a chemical equation reduction: process that gain electrons soluble: will dissolve