Chemical Reactions

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2 Chemical Reactions

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6 Agenda Day 39- Types of Chemical Reactions- Synthesis and Decomposition Lesson: PPT- Synthesis and decomposition Assign OBS. Table and Collect PreLAB Handouts: 1. Types of RxnHandout 2. Types of Rxn.Worksheet- Text: 1. P HW: Worksheets, P.161 # 1-8 Day 41- LAB- Types of Chemical Reactions Lesson: LAB HW: P.148 are you ready # 1-10 ( Unit 3)

7 Properties and Changes in Matter Physical property: a characteristic that can be observed or measured without changing the identity of the substance. Ex: melting point or boiling point Physical change: a change in a substance that does not involve a change in the identity of the substance. Ex: cutting, grinding, melting

8 Properties and Changes in Matter Chemical property: a substances ability to transform into different substances. Ex: ability iron has to rust by combing with the oxygen in air. Chemical change or chemical reaction: a change in a substance that involves it changing into a different substance. Ex: burning charcoal (carbon and oxygen) turns it into carbon dioxide. A chemical change or reaction is written as an equation: Carbon + Oxygen = Carbon Dioxide Reactants Products

9 Indicators of chemical reactions Emission of light or heat Formation of a gas Formation of a precipitate Color change Emission of odor

10 Steps to Writing Reactions Some steps for doing reactions 1. Identify the type of reaction 2. Predict the product(s) using the type of reaction as a model 3. Balance it Don t forget about the diatomic elements! (BrINClHOF) For example, Oxygen is O 2 as an element. In a compound, it can t be a diatomic element because it s not an element anymore, it s a compound!

11 Symbols used in equations (s) after the formula solid Cu (s) (g) after the formula gas H 2 (g) (l) after the formula -liquid H 2 O (l) (aq) after the formula - dissolved in water, an aqueous solution, CaCl 2 (aq) - used after a product indicates a gas (same as (g)) O 2 - used after a product indicates a solid (same as (s)) CaCO 3

12 Summary of Symbols

13 Types of Chemical Reactions: There are 5 main types listed below and the general formulas for each are given 1. combination (or synthesis) reaction A + B AB 2. decomposition AB A + B 3. single replacement A + BC AC + B 4. double replacement AB + CD AD + CB the positive ion is always written first. 5. combustion C x H y + O 2 CO 2 + H 2 O here oxygen is always a reactant and carbon dioxide and water are always products in a COMPLETE combustion reaction.

14 Decomposition A complex substance (compound) decomposes into 2 or more simple substances. Heat or electricity is usually required. General equation: AB A + B Ex: 2H 2 O 2H 2 + O 2 2NaCl 2 Na + Cl 2 8MgS 8Mg + S 8

15 Decomposition Reactions Another view of a decomposition reaction:

16 Special decomposition reactions to know: 2KClO 3 2KCl + 3O 2 - all metal chlorates decompose into metal chloride + O 2 Sr(ClO 3 ) 2 SrCl O 2 CaCO 3 CaO + CO 2 - metal carbonates decompose into a metal oxide + CO 2 Na 2 CO 3 Na 2 O + CO 2 2KOH K 2 O + H 2O - metal hydroxides decompose into a metal oxide + H 2 O Ca(OH) CaO + H 2 2 O 2HNO 3 N 2 O 5 + H 2 O - acids decompose into a non-metal oxide + H 2 O H 2 SO 3 SO 2 + H 2 O

17 A simulation of the reaction: 2H 2 + O 2 2H 2 O

18 Synthesis Where 2 or more simple substances (elements or compounds) combine to form ONE complex substance General equation: A + B AB Ex: 8Fe + S 8 8FeS 2Sr + O 2 2SrO Mg + Br 2 MgBr 2

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33 Translate Equation Aluminum metal reacts with liquid bromine to form solid aluminum bromide 2 Al(s) + 3 Br 2 (l) 2 AlBr 3 (s)

34 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)

35 Special Synthesis Reactions: Special Combination or Synthesis Reactions: When one of the metals that has a variable charge on it is an ion when Fe, Pb, Cu, or Sn combines with another substance, which charge do you use? Ex: Fe + O 2 FeO or Fe 2 O 3?????? Which is the correct product?? If one of these metals reacts with fluorine, oxygen, or nitrogen (F, O, N), these nonmetals will pull the metal to its HIGHEST charge or oxidation number. Otherwise, when these metals react in a combination reaction, use their LOWEST charge or oxidation number when forming a new compound.

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37 Special Synthesis reactions to know: 2NaCl + 3O 2 2NaClO 3 2KCl + 3O 2 2KClO 3 K 2 O + CO 2 K 2 CO 3 SrO + CO 2 SrCO 3 CaO + H 2 O Ca(OH) 2 Na 2 O + H 2 O 2 NaOH P 2 O 5 + 3H 2 O 2H 3 PO 4 P 2 O 3 + 3H 2 O 2H 3 PO 3

38 Learning Check Classify the following reactions as 1) combination or 2) decomposition: A. H 2 + Br 2 2HBr B. Al 2 (CO 3 ) 3 Al 2 O 3 + 3CO 2 C. 4 Al + 3C Al 4 C 3

39 Solution Classify the following reactions as 1) combination or 2) decomposition: _1_A. H 2 + Br 2 2HBr _2_B. Al 2 (CO 3 ) 3 Al 2 O 3 + 3CO 2 _1_C. 4 Al + 3C Al 4 C 3

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41 Agenda Day 42- Types of Chemical Reactions- Single displacement & Double displacement Lesson: PPT Handouts: 1. Types of RxnHandout ; 2. Types of Rxn.Worksheet- Text: 1. P & P , Oxides pg ; Neutralization page , HW: Worksheets, P.169 # 1-7; P.204 # 3-6; P. 177 # 1-7,P. 197 # 1-7,P. 210 # 1-3

42 Single displacement Example: Zn + CuCl 2 Cl Cu Cl + Zn Cl Zn Cl + Cu General: AB + C AC + B

43 Single Displacement Reactions Single Replacement Reactions occur when one element replaces another in a compound. A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-). element + compound element + compound A + BC AC + B (if A is a metal) OR A + BC BA + C (if A is a nonmetal) (remember the cation always goes first!) When H 2 O splits into ions, it splits into H + and OH - (not H+ and O -2!!)

44 We have looked at several reactions: Fe + CuSO 4 Cu + FeSO 4 Li + H 2 O LiOH + H 2 Such experiments reveal trends. The No, activity Ni is series ranks the relative reactivity Yes, below of metals. Li is Na It allows us to predict if certain chemicals above Zn will undergo single displacement reactions when mixed: metals near the top are most Yes, reactive Al is and will displace metals near the above bottom. Cu Q: Which of these will react? 2Fe + 3CuSO 4 2Cu + Fe Ni + NaCl 2 (SO Yes, 4 ) Fe is 3 NR (no reaction) above Cu 2Li + ZnCO 3 Zn + Li 2 CO 3 2Al + 3 CuCl 2 3Cu + 2AlCl 3 K Na Li Ca Mg Al Zn Fe Ni Sn Pb H Cu Hg Ag Au

45 H is the only nonmetal listed. H 2 may be displaced from acids or can be given off when a metal reacts with H 2 O (producing H 2 + metal hydroxide). The reaction with H 2 O depends on metal reactivity & water temp. Q: Will Mg react with H 2 O? cold H 2 O hot H 2 O steam A: No for cold, yes if it is hot/steam Mg + H 2 O H 2 + Mg(OH) 2 acid Q: Zn + HCl H 2 + ZnCl 2 Complete these reactions: 2Al + 6H 2 O(steam) 3H 2 + 2Al(OH) 3 Cu + H 2 O NR Ca + H 2 SO 4 H 2 + CaSO 4 2Na + 2H 2 O H 2 + 2NaOH K Na Li Ca Mg Al Zn Fe Ni Sn Pb H Cu Hg Ag Au

46 Please Send Little Charlie McArthy A Zebra In a Nice Tin Lined High Crate Marked Special Good Potassium Sodium Lithium Calcium Magnesium Aluminum Zinc Iron Nickel Tin Lead Hydrogen Copper Mercury Silver Gold K Na Li Ca Mg Al Zn Fe Ni Sn Pb H Cu Hg Ag Au

47 Other Activity Series Information All metals will have a specific place in the activity series. For simplicity, only the most common metals are shown. The metals near the top of the activity series are more reactive because their valence electrons are more easily removed. On tests and exams the activity series may appear as K, Na, Ag, Au; you must remember that K is reactive, Au is not. If the valence of a metal is not indicated in the question, use its most common valence (in bold on your periodic table) to determine the correct chemical formula.

48 Reactivity of halogens Certain nonmetals, the halogens, also behave like this. The order of strength of the halogens is F 2 Cl 2 Br 2 I 2 Decreasing strength Example: F 2 + CuCl 2 Cl 2 + CuF 2 I 2 + CuCl 2 No RXN!!!

49 Double displacement Example: MgO + CaS Mg O + Ca S Mg S + Ca O General: AB + CD AD + CB

50 Double Replacement Reactions Occur when the cations (positive ions) switch places. You do NOT need the activity series of metals list in these reactions. When you switch places, be sure to correctly write the formula of the new compound!! Think about it like foil ing in algebra, first and last ions go together + inside ions go together Example: AgNO 3(aq) + NaCl (s) AgCl (s) + NaNO 3(aq) Another example: 2 KMn0 4 + Na 2 C 2 O 4 2 NaMnO 4 + K 2 C 2 O 4

51 Special double displacement reactions to know: In these special DD reaction one of the two products decomposes. CaCO HCl CaCl 2 + H 2 CO 3 CO 2 + H 2 O K 2 SO 3 + 2HNO 3 2KNO 3 + H 2 SO 3 SO 2 + H 2 O NH 4 Cl + NaOH NaCl + NH 4 OH NH 3 + H 2 O

52 Acid/Base Reaction- Type of Double Displacement Reaction An acid and a base react to form a salt and water. Always in aqueous solution Acid (H + ) + Base (OH - ) Salt + H 2 O NaOH + HCl NaCl + H 2 O 2NH 4 OH + H 2 SO 4 (NH 4 ) 2 SO 4 + 2H 2 O

53 Learning Check Classify the following reactions as 1) single replacement 2) double replacement A. 2Al + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 3H 2 B. Na 2 SO 4 + 2AgNO 3 Ag 2 SO 4 + 2NaNO 3 C. 3C + Fe 2 O 3 2Fe + 3CO LecturePLUS Timberlake 99

54 Agenda Day 43- Types of Chemical Reactions- Activity Series LAB Lesson: Finish PPT & Activity Series LAB Handouts: 1. Types of RxnHandout ; 2. Types of Rxn.Worksheet- Text: 1. P & P , HW: Worksheets, P.169 # 1-7; P.204 # 3-6; P. 177 # 1-7,P. 197 # 1-7,P. 210 # 1-3

55 Activity series lab 1. On the next slide, place a check in the corner of boxes where you think reactions will take place. 2. Get a plastic spot plate. 3. Combine chemicals specified in the chart. Figure out a way to keep track of the chemicals. Use a ¼ scoop for solids (the less, the better). Use 1 squeeze of an eyedropper for solutions. 4. Write chemical equations for chemicals that reacted. Write NR where there was no reaction. 5. Dump used chemicals into the large funnel at the front of the room (use a squirt bottle to rinse remaining chemicals into the funnel). Wash the spot plate and glass rod very well. Dry & return.

56 AgNO 3 H 2 SO 4 Fe(NO 3 ) 3 CuCl 2 Mg Cu Zn Mg + 2AgNO 3 Cu + 2AgNO 3 Zn + 2AgNO 3 2Ag+ Mg(NO 3 ) 2 2Ag+ Cu(NO 3 ) 2 2Ag+ Zn(NO 3 ) 2 Mg + H 2 SO 4 Zn + H 2 SO 4 NR H 2 + MgSO 4 H 2 + ZnSO 4 3Mg+ 2Fe(NO 3 ) 3 3Zn+ 2Fe(NO 3 ) 3 NR 2Fe+ 3Mg(NO 3 ) 2 Mg + CuCl 2 Zn + CuCl 2 NR Cu + MgCl 2 Cu + ZnCl 2 2Fe+ 3Zn(NO 3 ) 2

57 Solution Classify the following reactions as 1) single replacement 2) double replacement 1_A. 2Al + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 3H 2 2_B. Na 2 SO 4 + 2AgNO 3 Ag 2 SO 4 + 2NaNO 3 1_C. 3C + Fe 2 O 3 2Fe + 3CO LecturePLUS Timberlake 99

58 Agenda Day 44- Types of Chemical Reactions- Combustion & Exo and Endo & Review Lesson: PPT Handouts: 1. Types of RxnHandout ; 2. Types of Rxn.Worksheet2- Text: 1. P HW: Worksheets, P.197 # 1-7; Review & extra practice pg # 29-71

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60 Combustion/Simple Oxidation Reactions Where oxygen reacts with another substance, usually a hydrocarbon, resulting in the release of energy, usually heat or light. A hydrocarbon is a compound containing carbon and hydrogen, although we will work with combustion reactions with compounds containing hydrogen, carbon and oxygen sometimes. There are 2 types of combustion reactions: Incomplete instead of CO 2 being produced, the products may be CO, CO 2 and/or C. Water is also a product Complete carbon dioxide and water are the only products CH 4 + 2O 2 CO 2 + 2H 2 O

61 Combustion Reactions 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) Notice that the products are all the same, in every reactions. Isn t that great? We could vary it a bit by adding in nitrogen ( burns to form NO 2 ) and sulfur ( burns to form SO 2 ).

62 Combustion Reactions Edgar Allen Poe s drooping eyes and mouth are potential signs of CO poisoning.

63 Learning Check Balance the following combustion equations: C 5 H 12 + O 2 CO 2 + H 2 O C 5 H O 2 5 CO H 2 O C 21 H 24 N 2 O 4 + O 2 CO 2 + H 2 O + NO 2 C 21 H 24 N 2 O O 2 21 CO H 2 O + 2 NO 2

64 Practice-Predict the products and balance the following equations. Hint: Balancing combustion reactions: balance the carbons first, balance the hydrogens next, balance the oxygens last. 1. C 3 H 8 + O 2 2. C 6 H 6 + O 2 3. C 1 2 H 22 o 11 + O 2 4. C 2 H 5 SH + O 2 5. C 2 H 5 OC 2 H 5 + O 2 (assume incomplete combustion for rxn. #6) 6. C 2 H 2 + O 2

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66 Energy in chemical reactions: Some reactions require more energy then is produced; others produce more energy then is required. A. Exothermic Reaction: a reaction that releases energy; energy is a product and is written on the right side of the arrow. 2H 2 + O 2 H 2 O + ENERGY B. Endothermic Reaction: a reaction that absorbs energy; energy is a reactant and is written on the left of the arrow. Ca CO 3 + ENERGY CaO + CO 2

67 How to recognize which type If you know the 5 basic types of reactions, predicting the products of chemical reactions is not difficult. The first thing you need to do is to look at the reactants and determine what type of reaction will probably occur. Always keep in mind the general formulas of the 5 types of reactions. Look at the reactants Element(E), Compound(C) E + E C E + C C + C Acid + Base Look at the Products CO 2 + H 2 O Synthesis Decomposition Single replacement Double replacement Acid/Base reaction( DD) Combustion

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