CHAPTER 4. Some Types of Chemical Reactions

Transcription

1 CHAPTER 4 Some Types of Chemical Reactions 1

2 Types of Chemical Reactions 2 Rusting iron is a common example of a combination reaction, where two or more substances combine to form a new compound. rust is iron (III) oxide (Fe 2 O 3 ) formed on these crews and bike from the combination of iron and oxygen under moist conditions.

3 Types of Chemical Reactions 3 Mercury (II) oxide is decomposed by heat, leaving the silvercolored element mercury behind as oxygen is driven off. This is an example of a decomposition reaction, 2 HgO 2 Hg + O 2

4 Chapter Goals - The Periodic Table: Metals, Nonmetals, and Metalloids - Aqueous Solutions: An Introduction - Reactions in Aqueous Solutions - Oxidation Numbers - Naming Some Inorganic Compounds - Classifying Chemical Reactions 4

5 The Periodic Table Mendeleev & Meyer Discovered the periodic law The properties of the elements are periodic functions of their atomic numbers. 5 Dmitri Mendeleev Lothar Meyer

6 Groups or Families 6 Vertical Columns: Vertical Columns: referred to as groups or families and have similar chemical and physical properties (e.g. similar kinds of reactions, and similar kinds of compounds).

7 Periods or Series 7 Horizontal Rows: Horizontal Rows: called periods or series and have properties that change progressively across the table (transition from metals to nonmetals).

8 Alkali and alkaline earth metals 8 Alkali metals Alkaline earth metals Halogens Noble gases

9 9 Periodic Table

10 The Periodic Table: Metals, Nonmetals, and Metalloids Some chemical properties of metals 1. Outer shells contain few electrons 2. Form cations by losing electrons 3. Form ionic compounds with nonmetals 4. Solid state characterized by metallic bonding 10

11 Similar Reactions Requires warm water; sluggish Consider Group I: Li, Na, K, Rb,, Cs Li + H 2 O explosive gas, alkaline solution Na + H 2 O explosive gas, alkaline solution K + H 2 O explosive gas, alkaline solution Rb + H 2 O explosive gas, alkaline solution Cs + H 2 O explosive gas, alkaline solution Vigorous in cool water; may explode Explosion likely; very dangerous Run! Call Our condolences.

12 The Periodic Table: Metals, Nonmetals, and Metalloids Some chemical properties of nonmetals 1. Outer shells contain four or more electrons 2. Form anions by gaining electrons 3. Form ionic compounds with metals and covalent compounds with other nonmetals 4. Form covalently bonded molecules; noble gases are monatomic 12

13 13 Metallic Character Mt 108 Hs 107 Bh 106 Sg 105 Db 104 Rf 89 Ac 88 Ra 87 Fr 86 Rn 85 At 84 Po 83 Bi 82 Pb 81 Tl 80 Hg 79 Au 78 Pt 77 Ir 76 Os 75 Re 74 W 73 Ta 72 Hf 57 La 56 Ba 55 Cs 54 Xe 53 I 52 Te 51 Sb 50 Sn 49 In 48 Cd 47 Ag 46 Pd 45 Rh 44 Ru 43 Tc 42 Mo 41 Nb 40 Zr 39 Y 38 Sr 37 Rb 36 Kr 35 Br 34 Se 33 As 32 Ge 31 Ga 30 Zn 29 Cu 28 Ni 27 Co 26 Fe 25 Mn 24 Cr 23 V 22 Ti 21 Sc 20 Ca 19 K 18 Ar 17 Cl 16 S 15 P 14 Si 13 Al 12 Mg 11 Na 10 Ne 9 F 8 O 7 N 6 C 5 B 4 Be 3 Li 2 He 1 H Metals Non-metals Metalloids

14 Metallic character increases Metallic character increases 14 Metallic Character

15 Aqueous Solutions: An Introduction Many reactions take place in water-aqueous solution. It is important to know what happens to substances when they are placed in water. 1. Is it soluble in water? 2. If it is soluble, does it break into ions? 3. Terminology: acid, base, and salt 15

16 Aqueous Solutions: An Introduction Electrolytes Classification of solutes: Nonelectrolytes: do not conduct electricity in water. The reason nonelectrolytes do not conduct electricity is because they do not form ions in solution. C 2 H 5 OH. Strong electrolytes: conduct electricity extremely well in dilute aqueous solutions. HCl, HNO 3, NaOH, KOH, NaCl, KBr etc. 16 Weak electrolytes : conduct electricity poorly in dilute aqueous solutions. CH 3 COOH.

17 17 Aqueous Solutions: An Introduction

18 Aqueous Solutions: An Introduction 1. Strong Acids Acids are substances that generate H + in aqueous solutions. HCl, HBr, HI, HNO 3, H 2 SO 4. Strong acids ionize 100% in water. 100% HCl H + Cl ( g ) ( aq ) ( aq ) + - HNO 3 + H O 2 l 100% H O () ( aq) ( aq) NO 3 18 or HNO 3 H O H 2 + ( aq) 3( aq) - +NO

19 Aqueous Solutions: An Introduction % HCl H + Cl ( g ) ( aq ) ( aq ) + -

20 Aqueous Solutions: An Introduction Some Strong Acids and Their Anions Formula Name 1. HCl hydrochloric acid 2. HBr hydrobromic acid 3. HI hydroiodic acid 4. HNO 3 nitric acid 5. H 2 SO 4 sulfuric acid 6. HClO 3 chloric acid 7. HClO 4 perchloric acid 20

21 Aqueous Solutions: An Introduction 2. Weak Acids Weak acids ionize significantly less than 100% in water. HF, CH 3 COOH, HCN, H 2 CO 3, H 2 SO 3, H 3 PO 4. Typically ionize 10% or less! CH 7% - + 3COOH CH3COO + H ( aq) ( aq) 21

22 Aqueous Solutions: An Introduction 22 Some Common Weak Acids Formula Name 1. HF hydrofluoric acid 2. CH 3 COOH acetic acid (vinegar) 3. HCN hydrocyanic acid 4. HNO 2 nitrous acid 5. H 2 CO 3 carbonic acid (soda water) 6. H 2 SO 3 sulfurous acid 7. H 3 PO 4 phosphoric acid 8. (COOH) 2 oxalic acid

23 23 Aqueous Solutions: An Introduction

24 Aqueous Solutions: An Introduction 3. Strong Bases Characteristic of common inorganic bases is that they produce OH - ions in solution. LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2, Sr(OH) 2, Ba(OH) 2 Similarly to strong acids, strong bases ionize 100% in water. KOH K + (aq) + OH - (aq) 24 Ba(OH) 2 Ba 2+ (aq) + 2 OH - (aq)

25 Aqueous Solutions: An Introduction 25 Common Strong Bases Formula Name 1. LiOH lithium hydroxide 2. NaOH sodium hydroxide 3. KOH potassium hydroxide 4. RbOH rubidium hydroxide 5. CsOH cesium hydroxide 6. Ca(OH) 2 calcium hydroxide 7. Sr(OH) 2 strontium hydroxide 8. Ba(OH) 2 barium hydroxide Notice that they are all hydroxides of IA and IIA metals

26 Aqueous Solutions: An Introduction 4. Insoluble or sparingly soluble bases Ionic compounds that are insoluble in water, consequently, not very basic. Formula Name 1. Cu(OH) 2 copper (II) hydroxide 2. Fe(OH) 2 iron (II) hydroxide 3. Fe(OH) 3 iron (III) hydroxide 4. Zn(OH) 2 zinc (II) hydroxide 5. Mg(OH) 2 magnesium hydroxide 26

27 Aqueous Solutions: An Introduction 5. Weak bases are covalent compounds that ionize slightly in water. Ammonia is most common weak base NH 3()g H O + 2 l () + NH 4 - (aq) +OH (aq) 27

28 Solubility Guidelines for Compounds in Aqueous Solutions Solubility: A compound that dissolves in water to an appreciable extent is soluble ; if not, it is insoluble 28 Solubility Rules: : rule 1 to rule 8 It is very important that you know these guidelines and how to apply them in reactions.

29 Solubility Guidelines for Compounds in Aqueous Solutions 1- Common inorganic acids and lowmolecular-weight organic acids are water soluble. High-molecular-weight organic acids are water insoluble All common compounds of the Group IA metal ions, Li +, Na +, K +, Rb +, Cs +, and the ammonium ion, NH 4+,are water soluble.

30 Solubility Guidelines for Compounds in Aqueous Solutions 3- Common nitrates, acetates, chlorates, and perchlorates are water soluble. NO 3-, CH 3 COO -, ClO 3-, and ClO (a) Common chlorides, Cl -, are water soluble. Exceptions AgCl, Hg 2 Cl 2,& PbCl 2 (b) Common bromides, Br -, and iodides, I -, behave similarly to chlorides. (c) Common fluorides, F -, are water soluble. Exceptions MgF 2, CaF 2, SrF 2, BaF 2, and PbF 2

31 Solubility Guidelines for Compounds in Aqueous Solutions Common sulfates, SO 4 2-, are water soluble. Exceptions PbSO, 4 BaSO, & 4 HgSO 4 Moderately soluble CaSO, 4 SrSO,& 4 Ag 2 SO 4 6- Common metal hydroxides, OH -, are water insoluble. Exceptions: group IA metals, LiOH, NaOH, KOH, RbOH & CsOH Exceptions: group IIA metals, beginning with Ca(OH) 2, Sr(OH) 2, and Ba(OH) B 2

32 Solubility Guidelines for Compounds in Aqueous Solutions 7- Common carbonates, CO 2-3, phosphates, PO 3-4, and arsenates, AsO 3-4, are water insoluble. Exceptions- group IA metals and NH 4+ plus Ca to Ba Moderately soluble MgCO Common sulfides, S 2-, are water insoluble. Exceptions group IA metals, group IIA metals, and NH + 4

33 Reactions in Aqueous Solutions There are three ways to write reactions in aqueous solutions. 1. Formula unit (molecular) equation: shows all reactants & products in molecular form (remember to balance) Zn (s) + CuSO 4(aq) ZnSO 4(aq) + Cu (s) 2. Total ionic equation: Show the ions and molecules as they exist in solution 33 Zn (s) +Cu 2+ +SO 2- Zn 2+ +SO ( aq) 4( aq) ( aq) 4( aq) (s) 2- + Cu

34 Reactions in Aqueous Solutions 3. Net ionic equation: shows ions that participate in reaction and removes spectator ions. Spectator ions: represented as < > s, do not participate in the reaction. The spectators can be cancelled off from both sides of the equation and the equation is reduced to the NET IONIC EQUATION. Zn (s) +Cu 2+ + SO 2- Zn 2+ SO ( aq) 4( aq) ( aq) 4( aq) (s) Cu 34 Zn (s) + Cu 2 + Zn 2+ + Cu ( aq) ( aq) (s)

35 Reactions in Aqueous Solutions 35 Molecular equation 2 HCl + Na SO 2 NaCl + H O + 2 H (aq) 2 3(aq) Total ionic reaction Cl Na 1+ (aq) ( aq) ( aq) ( aq) 3( aq) 2 Na Net ionic reaction SO 2 Cl H O SO ( l) 2( g) SO ( aq) ( aq) 2 ( l) 2( g) 2 H + SO H O + ( aq) 3( aq) 2 ( l) 2( g) + SO

36 Reactions in Aqueous Solutions Molecular equation Ca(OH) Ca HNO Ca(NO (aq) 3(aq) 3) + 2 H 2(aq) 2O( l) Total ionic equation OH H NO - Ca ( aq) ( aq) ( aq) 3( aq) ( aq) 3( aq) 2 ( l) Net ionic equation NO H O 2 OH H + ( aq ) ( aq ) 2 H 2 O ( l ) 36 OH - or better + + H H O ( aq ) ( aq ) 2 ( ) l

37 Reactions in Aqueous Solutions Molecular equation Ca(NO Ca 3) + K 2(aq) 2CO 2 KNO + CaCO 3(aq) 3(aq) 3(s) Total ionic reaction NO K ( aq) 3( aq) ( aq) 3( aq) Net ionic reaction 2 K CO 2-2 NO - + CaCO ( aq) 3( aq) 3( s) 37 Ca 2+ + CO 2- CaCO ( aq) 3( aq) 3(s)

38 Reactions in Aqueous Solutions Molecular equation 3CaCl ( ) 4 2(s) Na (aq) 3PO 6 NaCl 4(aq) (aq) + Ca3 PO Total ionic reaction 3Ca Cl Na 1+ ( aq) ( aq) ( aq) 4( aq) Net ionic reaction 6 Na PO 6Cl Ca PO ( ) ( aq) ( aq) 3 4 2() s Ca + 2 PO Ca PO ( ) ( aq ) 4( aq ) 3 4 2() s

39 Oxidation Numbers Many reactions, called oxidation-reduction or redox reactions, involve the transfer of electrons from 1 species to another. In order to keep track of the number of electrons lost or gained during a redox reaction, the concept of oxidation number is used. 39

40 Oxidation Numbers Guidelines for assigning oxidation numbers: 1. The oxidation number of any free, uncombined element is zero. Na, Be, K, Pb, H 2, O 2, P 4 = 0 2. The oxidation number of an element in a simple (monatomic) ion is the charge on the ion. 40 Li +, Li = +1; Fe 3+, Fe = +3; O 2-, O = -2

41 Oxidation Numbers 3. In the formula for any compound, the sum of the oxidation numbers of all elements in the compound is zero. 4. In a polyatomic ion, the sum of the oxidation numbers of the constituent elements is equal to the charge on the ion. 41

42 Oxidation Numbers 5. Fluorine, F, has an oxidation number of 1 in its compounds. 6. Hydrogen, H, has an oxidation number of +1 unless it is combined with metals, where it has the oxidation number -1. Examples LiH, BaH 2 7. Oxygen, O, usually has the oxidation number -2. Exceptions: In peroxides O has oxidation number of Examples - H 2 O 2, CaO 2, Na 2 O 2 In OF 2 O has oxidation number of +2.

43 Oxidation Numbers 8. Use the periodic table to help with assigning oxidation numbers of other elements. a. IA metals have oxidation numbers of +1. b. IIA metals have oxidation numbers of +2. c. IIIA metals have oxidation numbers of +3. There are a few rare exceptions. d. VA elements have oxidation numbers of 3 in binary compounds with H, metals or NH 4+. e. VIA elements below O have oxidation numbers of 2 in binary compounds with H, metals or NH Summary in Table 4-10.

44 Oxidation Numbers Assign oxidation numbers to each element in the following compounds: - N in NaNO 3 - B in BO 3 - -Snin K 2 Sn(OH) 6 - P in H 3 PO 4 - S in SO Cr in Cr 2 O N in NH 3 -Fe - P in H 4 P 2 O 7 - Hg in Hg 2 Cl 2 - Li in LiH - S in S 4 O C in HCO C in C 6 H 6

45 Oxidation Numbers NaNO 3 Na = +1 (Rule 8) O = -2 (Rule 7) N = +5 Calculate using rule (-2) + x = 0 45 x = +5

46 Oxidation Numbers 46 K 2 Sn(OH) 6 K = +1 (Rule 8) O = -2 (Rule 7) H = +1 (Rule 6) Sn = +5 Calculate using rule 3. 2(+1) + 6(-2) + 6(+1) + x = 0 x = +5

47 Oxidation Numbers SO 2-3 O = -2 (Rule 7) S = +4 Calculate using rule 4. 3(-2) + x = -2 x = +4 47

48 Oxidation Numbers Cr 2 O 7 2- O = -2 Cr = +6 You do it! 48

49 Oxidation number HCO - 3 O = -2 H = +1 3x(-2) + 1 +? = -1 C = +4 49

50 50 Oxidation Numbers Assign oxidation numbers to each element in the following compounds: - N in NaNO 3 - B in BO 3- (B = +5) -Snin K 2 Sn(OH) 6 - P in H 3 PO 4 (P = +5) - S in SO Cr in Cr 2 O 7 2- (Cr = +6) - N in NH 3 (N = -3) -Fe (Fe = 0) - P in H 4 P 2 O 7 (P = +5) - Hg in Hg 2 Cl 2 (Hg = +1) - Li in LiH (Li = +1) - S in S 4 O 6 2- (S = +2.5) - C in HCO C in C 6 H 6 (C = -1)

51 Oxidation States of Nitrogen HNO 3 NH 3 HNO 2 NO N 2 O N 2 HN 3 N 2 H Oxidation -1/ Reduction 51

52 Oxidation States of Chlorine HClO 4 HClO 2 HCl HClO 3 ClO 2 HClO Cl Oxidation +7-1 Reduction 52

53 Oxidation States of Sulfur S 2 O 8 2- H 2 S SO 4 2- S 2 O 6 2- SO 2 S 2 O 3 2- S 8 or S Oxidation +7-2 Reduction 53

54 Naming Some Inorganic Compounds 54 This is definitely IMPORTANT! Binary compounds are made of two elements. metal + nonmetal = ionic compound nonmetal + nonmetal = covalent compound Name the more metallic element first. Use the element s name. Name the less metallic element second. Add the suffix ide to the element s stem.

55 Naming Some Inorganic Compounds 55 Binary Ionic Compounds are made of a metal cation and a nonmetal anion. Cation named first Anion named second LiBr MgCl 2 lithium bromide magnesium chloride Li 2 S lithium sulfide Al 2 O 3 aluminum oxide Na 3 P sodium phosphide Mg 3 N 2 magnesium nitride

56 Naming Some Inorganic Compounds Binary ionic compounds containing metals that exhibit more than one oxidation state Metals exhibiting multiple oxidation states are: 1. most of the transition metals 2. metals in groups IIIA (except Al), IVA, & VA 56

57 Naming Some Inorganic Compounds There are two methods to name these compounds. 1. Older method add suffix ous to element s Latin name for lower oxidation state add suffix ic to element s Latin name for higher oxidation state 2. Modern method 57 use Roman numerals in parentheses to indicate metal s oxidation state

58 Naming Some Inorganic Compounds Compound Old System Modern System FeBr 2 ferrous bromide iron(ii) bromide FeBr 3 ferric bromide iron(iii) bromide SnO stannous oxide tin(ii) oxide SnO 2 stannic oxide tin(iv) oxide TiCl 2 titanous chloride titanium(ii) chloride TiCl 3 titanic chloride titanium(iii) chloride TiCl 4 does not work titanium(iv) chloride 58

59 Naming Some Inorganic Compounds Pseudobinary ionic compounds There are three polyatomic ions that commonly form binary ionic compounds. Anion 1. OH - hydroxide 2. CN - cyanide Cation 1. NH 4+ ammonium 59 Use binary ionic compound naming system.

60 Naming Some Inorganic Compounds 60 KOH Ba(OH) 2 Fe(OH) 2 Fe(OH) 3 Ba(CN) 2 NH 4 CN (NH 4 ) 2 S NH 4 CN potassium hydroxide barium hydroxide iron (II) hydroxide iron (III) hydroxide barium cyanide ammonium cyanide ammonium sulfide ammonium cyanide

61 Naming Some Inorganic Compounds 61 Binary covalent molecular compounds composed of two nonmetals other than hydrogen Nomenclature must include prefixes that specify the number of atoms of each element in the compound.

62 Naming Some Inorganic Compounds 62 Formula CO CO 2 SO 3 OF 2 P 4 O 6 P 4 O 10 Name (mono)carbon monoxide carbon dioxide sulfur trioxide oxygen difluoride tetraphosphorus hexoxide tetraphosphorus decoxide

63 Naming Some Inorganic Compounds The oxides of nitrogen illustrate why covalent compounds need prefixes and ionic compounds do not. Formula Old Name Modern Name N 2 O nitrous oxide dinitrogen monoxide NO nitric oxide nitrogen monoxide N 2 O 3 nitrogen trioxide dinitrogen trioxide NO 2 nitrogen dioxide nitrogen dioxide N 2 O 4 nitrogen tetroxide dinitrogen tetroxide N 2 O 5 nitrogen pentoxide dinitrogen pentoxide 63

64 Naming Some Inorganic Compounds 64 Binary Acids are binary compounds consisting of hydrogen and a nonmetal (group VIA element other than O or group VIIA elements). Compounds are usually gases at room temperature and pressure. Nomenclature for the gaseous compounds is hydrogen (stem)ide. When the compounds are dissolved in water they form acidic solutions. Nomenclature for the acidic solutions is hydro (stem)ic acid.

65 Naming Some Inorganic Compounds Formula Name Aqueous solution HF hydrogen fluoride hydrofluoric acid HCl hydrogen chloride hydrochloric acid HBr hydrogen bromide hydrobromic acid H 2 S hydrogen sulfide hydrosulfuric acid 65

66 Naming Some Inorganic Compounds 66 Ternary Acids and Their Salts are made of three elements, H, O, & a nonmetal. Two of the compounds are chosen as the basis for the nomenclature system. Higher oxidation state for nonmetal is named (stem)ic acid. Lower oxidation state for nonmetal is named (stem)ous acid Salts are named based on the acids. Anions of -ic acids make ate salts. Anions of -ous acids make ite salts.

67 Naming Some Inorganic Compounds 67 Memorize the names and formulas of these acids.

68 Naming Some Inorganic Compounds Name Formula carbonic acid H 2 CO 3 nitric acid HNO 3 boric acid H 3 BO 3 phosphoric acid H 3 PO 4 sulfuric acid H 2 SO 4 chloric acid HClO 3 bromic acid HBrO 3 iodic acid HIO 3 68 silicic acid H 4 SiO 4

69 Naming Some Inorganic Compounds Salts are formed by the reaction of the acid with a strong base. Acid Salt HNO 2 NaNO 2 nitrous acid sodium nitrite HNO 3 NaNO 3 nitric acid sodium nitrate H 2 SO 3 Na 2 SO 3 sulfurous acid sodium sulfite H 2 SO 4 Na 2 SO4 sulfuric acid sodium sulfate HClO 2 NaClO 2 chlorous acid sodium chlorite 69 HClO 3 NaClO 3 chloric acid sodium chlorate

70 Naming Some Inorganic Compounds Acids that have a higher oxidation state than the ic acid are given the prefix per. These acids and salts will have one more O atom than the ic acid. Acids that have a lower oxidation state than the ous acid are given the prefix hypo. 70 These acids and salts will have one less O atom than the ic acid.

71 71 Naming Some Inorganic Compounds

72 Naming Some Inorganic Compounds Increasing Oxid. # of chlorine atom 72 Acid Na Salt HClO (Cl = +1) NaClO hypochlorous acid sodium hypochlorite HClO 2 (Cl = +3) NaClO 2 chlorous acid sodium chlorite HClO 3 (Cl = +5) NaClO 3 chloric acid sodium chlorate HClO 4 (Cl = +7) NaClO 4 perchloric acid sodium perchlorate Increasing # of O atoms on Cl atom

73 Naming Some Inorganic Compounds 73 Acidic Salts are made from ternary acids that retain one or more of their acidic hydrogen atoms. Made from acid base reactions where there is an insufficient amount of base to react with all of the hydrogen atoms. Old system used the prefix bi to denote the hydrogen atom. Modern system uses prefixes and the word hydrogen.

74 Naming Some Inorganic Compounds NaHCO 3 Old system sodium bicarbonate Modern system sodium hydrogen carbonate KHSO 4 Old system potassium bisulfate Modern system potassium hydrogen sulfate KH 2 PO 4 Old system potassium bis biphosphate Modern system potassium dihydrogen phosphate 74 K 2 HPO 4 Old system potassium biphosphate Modern system potassium hydrogen phosphate

75 Classifying Chemical Reactions 75 Oxidation-Reduction Reactions (Redox reactions) Combination Reactions Decomposition Reactions Displacement Reactions Metathesis Reactions Acid-Base (neutralization) Reactions Precipitation reactions

76 Classifying Chemical Reactions YES Reaction Change in Oxidation State? NO Redox Metathesis or Decomposition Displacement:M+2HCl MCl 2 +H 2 (g) Decomposition:A B + C +. Combination:A + B C Disproportionation:M + M 3+ +M 0 76 Metathesis Neutralization:H + +OH - H 2 O Precipitation:Ag + +Cl - AgCl(s) Decomposition No change in OS

77 Oxidation-Reduction Reactions Oxidation is an increase in the oxidation number. Corresponds to the loss of electrons. Reduction is a decrease in the oxidation number. Corresponds to the gain of electrons 77

78 Oxidation-Reduction Reactions 78 Oxidizing agents are chemical species that: 1. oxidize some other substance 2. contain atoms that are reduced 3. gain electrons Reducing agents are chemical species that: 1. reduce some other substance 2. contain atoms that are oxidized 3. lose electrons

79 Oxidation-Reduction Reactions: Example of oxidation-reduction or redox reaction. Combustion reactions are redox reactions Combustion of Mg Mg is oxidized to MgO O 2 is reduced to O 2-2Mg + O 2 2MgO 79

80 Combination Reactions 80 Combination reactions occur when two or more substances combine to form a compound. There are three basic types of combination reactions. 1. Two elements react to form a new compound 2. An element and a compound react to form one new compound 3. Two compounds react to form one compound

81 Combination Reactions 1. Element + Element Compound A. Metal + Nonmetal Binary Ionic Compound 2 Na + Cl 2 NaCl ( s) 2( g) ( s) 2 Mg + O 2 MgO ( s ) 2( g ) ( s ) B. Nonmetal + Nonmetal Covalent Binary Compound P + 5 O P O 4 () s 2( g ) 4 10 () s 81 P + 6 Cl 4 PCl 4 () s 2( g) 3() l

82 Combination Reactions 2. Compound + Element Compound AsCl + Cl AsCl 3 SF () s 2( g) 5() s + F SF 4 ( s) 2( g) 6( g) 3. Compound + Compound Compound Li 2O + SO 2 Li 2SO 3 82 NH3 + HCl NH Cl ( g) ( g) 4 ( s)

83 Disproportionation Reactions Disproportionation raction is a redox reaction in which the same element is oxidized and reduced. 83

84 Decomposition Reactions Decomposition reactions occur when one compound decomposes to form: 1. Two elements 2. One or more elements and one or more compounds 3. Two or more compounds 84

85 Decomposition Reactions 1. Compound Element + Element 2 N + O 2 N O 2 ( g) 2( g) 2( g) 2. Compound Element + Compound(s) 2 H 3+ hν or Fe or Mn 2O2 2 H O + O ( aq) 2 ( l) 2( g) 3. Compound Compounds 85 NH + 4HCO3 NH + H O CO ( s) 3( g) 2 ( g) 2( g)

86 Displacement Reactions Displacement reactions occur when one element displaces another element from a compound. 2AgNO 3 (aq) + Cu(s) Cu(NO 3 ) 2 + 2Ag 86

87 Displacement Reactions The following metals are active enough to displace hydrogen K, Ca, Na, Mg, Al, Zn, Fe, Sn, & Pb 2 Al + 3H SO Al (s) 2 4 (SO + 3 H ( aq) 2 4 3( aq) 2( g) ) 87

88 Displacement Reactions Each halogen will displace less active (heavier) halogens from their binary salts; that is, the order of decreasing activities is F 2 > Cl 2 > Br 2 > I 2 Cl + 2 NaI I + 2 NaCl 2 ( g ) ( aq ) 2( s ) (aq) 88

89 Metathesis Reactions 89 Metathesis reactions occur when two ionic aqueous solutions are mixed and the ions switch partners. AX + BY AY + BX Metathesis reactions remove ions from solution in two ways: 1. form unionized molecules like H 2 O 2. form an insoluble solid Ion removal is the driving force of metathesis reactions.

90 Metathesis Reactions 1. Acid-Base (neutralization) Reactions Formation of the nonelectrolyte H 2 O acid + base salt + water HCl + NaOH NaCl + H 2 O 2. Precipitation reactions are metathesis reactions in which an insoluble compound is formed. 90

91 Classifying Chemical Reactions Which of the following is a reduction-oxidation (redox) reaction? FeCl 2 (aq) + 2AgNO 3 (aq) 2AgCl(s) + Fe(NO 3 ) 2 (aq) AgNO 3 (aq) + NaBr(aq) AgBr(s) + NaNO 3 (aq) Zn(s) + 2AgNO 3 (aq) 2Ag(s) + Zn(NO 3 ) 2 (aq) CaO(s) + CO 2 (g) CaCO 3 (s) 3HCl(aq) + Cr(OH) 3 (s) CrCl 3 (aq) + 3H 2 O(l) 91

92 Classifying Chemical Reactions Which of the following reactions is a combination reaction? (a) AgNO 3 (aq) + HCl(aq) AgCl(s) + HNO 3 (aq) (b) Na 2 O(s) + CO 2 (g) (c) C 3 H 8 (g) + 5O 2 (g) (d) 2H 2 O(l) Na 2 CO 3 (s) 2H 2 (g) + O 2 (g) (e) KOH(aq) + HCl(aq) 3CO 2 (g) + 4H 2 O(l) KCl(aq) + H 2 O(l) 92

93 Naming Compounds Write formulas for the compounds that are expected to be formed by the following pairs of ions: 93

94 Homework Assignment One-line Web Learning (OWL): Chapter 4 Exercises and Tutors Required Due by 03/08 (11:00 pm). 94