Worksheet # 11 1. A solution of sodium chloride is mixed with a solution of lead (II) nitrate. A precipitate of lead (II) chloride results, leaving a solution of sodium nitrated. Determine the class of reaction. The choices are decomposition, combination, singledisplacement, double-displacement, and combustion. 2. Solid sulfur is ignited and burns in oxygen gas with a blue flame to form sulfur dioxide. Determine the class of reaction. The choices are decomposition, combination, single-displacement, double-displacement, and combustion. 3. Balance the following equations and classify the reactions as decomposition, combination, single-displacement, double-displacement, or combustion. a. GaH 3 + N(CH 3 ) 3 (CH 3 ) 3 NGAH 3 b. GeCl 2 + Cl 2 GeCl 4 c. N 2 (g) + CaC 2 (s) C (s) + CaNCN d. N 2 (g) + Mg (s) Mg 3 N 2 e. NH 4 Cl (s) NH 3 (g) + HCl (g) f. CaO (s) + SO 3 CaSO 4 (s) g. PCl 5 (g) PCl 3 (g) + Cl 2 (g) h. Ca 3 N 2 (s) + H 2 O (l) Ca(OH) 2 (aq) + NH 3 (g) 4. When heated, nickel (II) carbonate undergoes a decomposition reaction. Write a balanced equation to describe this reaction 5. When heated, platinum (IV) chloride undergoes a decomposition reaction. Write a balanced equation to describe this reaction 6. Complete and balance the equation for the following decomposition reactions. All reactions are heated. a. Cu(OH) 2 (s) b. HgO (s) 7. Sodium metal reacts with chlorine gas in a combination reaction. Write a balanced equation to describe this reaction. 8. Complete and balance each of the following combination reactions: a. Li 2 O (s) + H 2 O (l) b. SO 2 (g) + O 2 (g) c. CaO (s) + H 2 O (l) 9. Zinc metal reacts with a solution of tin (II) chloride in a single- replacement reaction. Write a balanced equation to describe this reaction. 10. Iron metal reactions with a solution of copper (II) sulfate in a single-displacement reaction. Write a balanced equation to describe this reaction. Worksheet 11 1
11. Consider the following metals. Determine which will react with water and which will react with a solution of hydrochloric acid. Write a balanced equation to describe any equation that occurs. a. Cr b. Bi c. K 12. Complete and balance each of the following single-displacement reactions. a. Al (s) + CuSO 4 (aq) b. Cs (s) + H 2 O (l) 13. Which of the following single-replacement reactions will actually occur if the indicated reagents are mixed? a. Ni (s) + FeCl 2 (aq) NiCl 2 (aq) + Fe (s) b. 2 Al (s) + 3 NiCl 2 (aq) 2 AlCl 3 (aq) + 3 Ni (s) c. Fe (s) + CuCl 2 (aq) FeCl 2 (aq) + Cu (s) d. 3 Sn (s) + 2 AlCl 2 (aq) 3 SnCl 2 (aq) + 2 Al Answers to Worksheet # 11 1. From the description we learn that the there are two reactants: sodium chloride and lead(ii) nitrate. These are both compounds. There are also two products: lead(ii) chloride and sodium nitrate. Since these are also compounds, the reaction is double-displacement (2 compounds as reactants and 2 compounds as products). 2. The reactants are solid sulfur and oxygen gas. These are both elements. Since there is only one product, sulfur dioxide, which is a compound, this is a combination reaction (2 elements or compounds as reactants and 1compound as the product). 3. For help classifying reactions, refer to Table 5.1 (Bauer p. 167). We can classify two of the types on the number of products and reactants in the chemical equation. In combination reactions, 2 substances combine to form 1 new substance; in decomposition reactions, 1 compound forms several new substances. Equations indicating 2 reactants and 2 products represent either single- or double-displacement reactions. If 1 of the reactants and 1 of the products is an element, the reaction is single-displacement. (a) combination: GaH 3 + N(CH 3 ) 3 (CH 3 ) 3 NGaH 3 (b) combination: GeCl 2 + Cl 2 GeCl 4 (c) single-displacement: N 2 (g) + CaC 2 (s) 2C(s) + CaNCN(s) (d) combination: N 2 (g) + 3Mg(s) Mg 3 N 2 (s) (e) decomposition: NH 4 Cl(s) NH 3 (g) + HCl(g) (f) combination: CaO(s) + SO 3 (g) CaSO 4 (s) (g) decomposition: PCl 5 (g) PCl 3 (g) + Cl 2 (g) (h) double-displacement: Ca 3 N 2 (s) + 6H 2 O(l) 3Ca(OH) 2 (aq) + 2NH 3 (g) Worksheet 11 2
4. Carbonate-containing compounds (except Group IA (1)), when heated, produce the metal oxide and carbon dioxide gas (Table 5.2). In this case, we know that nickel has a 2+ charge to balance the charge of the 2 carbonate ion. The oxide will be NiO. The balanced chemical equation is NiCO 3 (s) NiO(s) + CO 2 (g). 5. When chloride-containing compounds are heated they decompose, forming chlorine gas and the elemental metal (Table 5.2). In this case, platinum(iv) chloride, PtCl 4, decomposes to produce platinum metal, Pt, and chlorine gas, Cl 2. The balanced chemical equation is PtCl 4 (s) Pt(s) + 2Cl 2 (g). Note: Most ionic compounds (such as PtCl 4 ) are solids, and molecular chlorine is a gas. 6. See Table 5.2 (Bauer p 168). (a) Cu(OH) 2 (s) CuO(s) + H 2 O(g) Hydroxides decompose to the metal oxide with the loss of water (as a vapor or gas). Even at the high temperatures needed to decompose many of these compounds, ionic compounds remain in the solid state. (b) 2HgO(s) 2Hg(l) + O 2 (g) Oxides of Au, Pt, and Hg decompose to the pure metal and oxygen gas. 7. 2Na(s) + Cl 2 (g) 2NaCl(s) Combination reactions result in the formation of 1 product from 2 reactants. If the reactants are a metal and a nonmetal, we can reliably predict that the metal will form a cation and the nonmetal will form an anion. When molecular chlorine, Cl 2, reacts with metals, the chlorides of the metals are formed. Sodium is a Group IA (1) metal so it will form a 1+ ion. The formula for chloride ion is Cl. The formula for the metal chloride is NaCl (salt). 8. Combination reactions result in the formation of 1 product from 2 reactants. (a) Li 2 O(s) + H 2 O(l) 2LiOH By combining Li 2 O and H 2 O we could arrive at several different products. Metal oxides combine with water to form hydroxides. In this case, the hydroxide would result from the combination of lithium ions, Li +, and hydroxide ions, OH. The product for this reaction is LiOH. (b) 2SO 2 (g) + O 2 (g) 2SO 3 (g) By combining the SO 2 and O 2 we could arrive at several different products (either SO 4 or SO 3 ). In this case, the correct product is SO 3. (c) CaO(s) + H 2 O(l) Ca(OH) 2 (aq) By combining CaO and H 2 O we could arrive at several different products. Metal oxides combine with water to form hydroxides. In this case, the Worksheet 11 3
hydroxide would result from the combination of calcium ions, Ca 2+, and hydroxide ions, OH. The product for this reaction is Ca(OH) 2. 9. In a single-displacement reaction, 1 element displaces its ionic counterpart from a compound. That is, a metal displaces the metal ion or a nonmetal displaces the nonmetal ion. The formulas for the products are determined by the element or ions that are produced (i.e. metal or diatomic molecules, etc.). When Zn displaces Sn, Zn will form a 2+ ion (Figure 3.12). In this single-displacement reaction, the formula for the anion remains unchanged. Since the formula for chloride ion is Cl, the product is ZnCl 2. The balanced equation is: Zn(s) + SnCl 2 (aq) ZnCl 2 (aq) + Sn(s) 10. In a single-displacement reaction, 1 element displaces its ionic counterpart from a compound. That is, a metal displaces the metal ion or a nonmetal displaces the nonmetal ion. The formulas for the products are determined by the element or ions that are produced (i.e. metal or diatomic molecules, etc.). When Fe displaces Cu, Fe will form a 2+ ion. In this single-displacement reaction, the formula for the anion remains unchanged. Fe(s) + CuSO 4 (aq) Cu(s) + FeSO 4 (aq) 11. In reactions of metals with hydrochloric acid solutions or water, one product will always be hydrogen gas (H 2 ). To determine whether a reaction takes place, compare the activity of the metal (not the metal ion found in the product) with the activity of hydrogen gas (Figure 5.21). If the metal is higher in the activity series than hydrogen gas, a reaction will take place. Some metals are more active than others. Those that are more active react under less extreme conditions. (a) Cr is more active than H 2. This means that it can displace hydrogen under the right conditions. However, Cr is not active enough to displace hydrogen in cold water. Either hydrochloric acid solution or steam is required to cause a reaction. Chromium forms a 2+ ion in the activity series. Cr reacts with HCl: Cr(s) + 2HCl(aq) CrCl 2 (aq) + H 2 (g) Cr reacts with steam: Cr(s) + 2H 2 O(g) ----> Cr(OH) 2 (s) + H 2 (g) 12 In a single-displacement reaction, 1 element displaces its ionic counterpart from a compound. That is, a metal displaces the metal ion, or a nonmetal displaces the nonmetal ion. To determine whether a reaction occurs, we compare the activities of the metals involved (Figure 5.21). If the metal is more active than the metal whose ion appears in the compound, a reaction occurs. In these cases, the formula for the ionic product is determined by the metal ion that is produced. If you can t predict the charge (i.e. it is not listed in Figure 3.12), assume that it has a charge of 2+. For example if Fe displaces Cu, Fe will form a 2+ ion. In this type of single-displacement reaction, the formula for the anion remains unchanged. (a) Al (s) higher on the activity series than Cu so a reaction occurs. Al forms a 3+ ion, and Cu 2+ is displaced as copper metal, Cu(s). 2Al(s) + 3CuSO 4 (aq) Al 2 (SO 4 ) 3 (aq) + 3Cu(s) Worksheet 11 4
(b) Cs is higher in activity than H 2 so a reaction occurs. In reactions of active metals with water, hydrogen gas is formed. Cs forms a 1+ ion, and H + is displaced as H 2 (g). When metals displace H + from H 2 O (or HOH), the product is a metal hydroxide. 2Cs(s) + 2H 2 O(l) 2CsOH(aq) + H 2 (g) 13. In a single displacement reaction, 1 element displaces its ionic counterpart from a compound. That is, a metal displaces the metal ion, or a nonmetal displaces the nonmetal ion. To determine whether a reaction occurs, we compare the activities of the metals involved (Figure 5.21). If the metal is more active than the metal whose ion appears in the compound, a reaction occurs. (a) Nickel is less active than iron. No reaction occurs. (b) Aluminum is more active than nickel. The reaction occurs. (c) Iron is more active than copper. The reaction occurs. (d) Tin is less active than aluminum. No reaction occurs Worksheet 11 5