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Chemical Reactions

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Chemical Reactions

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  1. Chemical Reactions

  2. 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.156-161 • 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)

  3. 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…

  4. 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

  5. Indicators of chemical reactions • Emission of light or heat • Formation of a gas • Formation of a precipitate • Color change • Emission of odor

  6. Steps to Writing Reactions Some steps for doing reactions • Identify the type of reaction • Predict the product(s) using the type of reaction as a model • Balance it Don’t forget about the diatomic elements! (BrINClHOF) For example, Oxygen is O2 as anelement. In a compound, it can’t be a diatomic element because it’s not an element anymore, it’s a compound!

  7. Symbols used in equations • (s) after the formula –solid Cu(s) • (g) after the formula –gas H2 (g) • (l) after the formula -liquid H2O(l) • (aq) after the formula - dissolved in water, an aqueous solution, CaCl2 (aq) • - used after a product indicates a gas (same as (g)) O2 • - used after a product indicates a solid (same as (s)) CaCO3

  8. Summary of Symbols

  9. 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 CxHy + O2  CO2 + H2O here oxygen is always a reactant and carbon dioxide and water are always products in a COMPLETE combustion reaction.

  10. Decomposition A complex substance (compound) decomposes into 2 or more simple substances. Heat or electricity is usually required. General equation: AB  A + B Ex: 2H2O 2H2 + O2 2NaCl  2 Na + Cl2 8MgS  8Mg + S8

  11. Decomposition Reactions • Another view of a decomposition reaction:

  12. Special decomposition reactions to know: 2KClO3  2KCl + 3O2- all metal chlorates decompose into metal chloride + O2 Sr(ClO3)2  + CaCO3 CaO + CO2 - metal carbonates decompose into a metal oxide + CO2 Na2CO3  + 2KOH K2O + H2O - metal hydroxides decompose into a metal oxide + H2O Ca(OH)2 + 2HNO3 N2O5+ H2O - acids decompose into a non-metal oxide + H2O H2SO3  +

  13. A simulation of the reaction: 2H2 + O2   ® 2H2O  

  14. Synthesis Where 2 or more simple substances (elements or compounds) combine to form ONE complex substance General equation: A + B  AB Ex: 8Fe + S8 8FeS 2Sr + O2  2SrO Mg + Br2 MgBr2

  15. Translate Equation Aluminum metal reacts with liquid bromine to form solid aluminum bromide 3 2 ___ Al(s) 2 + ___ Br2(l) →___ AlBr3(s)

  16. Practice • Predict the products. Write and balance the following synthesis reaction equations. • Sodium metal reacts with chlorine gas Na(s) + Cl2(g)  • Solid Magnesium reacts with fluorine gas Mg(s) + F2(g)  • Aluminum metal reacts with fluorine gas Al(s) + F2(g) 

  17. 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 + O2FeO or Fe2O3 ?????? 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 chargeoroxidation number. Otherwise, when these metals react in a combination reaction, use their LOWEST charge or oxidation number when forming a new compound.

  18. Special Synthesis reactions to know: 2NaCl + 3O2  2NaClO3 KCl+ O2 K2O + CO2 K2CO3 SrO+ CO2 CaO+ H2O  Ca(OH)2 Na2O + H2O  P2O5 + 3H2O  2H3PO4 P2O3+ H2O 

  19. Learning Check Classify the following reactions as 1) combination or 2) decomposition: ___A. H2 + Br2 2HBr ___B. Al2(CO3)3 Al2O3+ 3CO2 ___C. 4 Al + 3C  Al4C3

  20. Solution Classify the following reactions as 1) combination or 2) decomposition: _1_A. H2 + Br2 2HBr _2_B. Al2(CO3)3 Al2O3+ 3CO2 _1_C. 4 Al + 3C  Al4C3

  21. 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.164-168 & P. 172-177, Oxides pg 200-204; Neutralization page 206-211, • HW: Worksheets, P.169 # 1-7; P.204 # 3-6; P. 177 # 1-7,P. 197 # 1-7,P. 210 # 1-3

  22. + +  Cl Cl Cl Cl Zn Zn Cu Cu Single displacement Example: Zn + CuCl2 General: AB + C  AC + B

  23. 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 H2O splits into ions, it splits into H+ and OH- (not H+ and O-2 !!)

  24. No, Ni is below Na Yes, Li is above Zn Yes, Al is above Cu Yes, Fe is above Cu We have looked at several reactions: Fe + CuSO4  Cu + FeSO4 Li + H2O  LiOH + H2 Such experiments reveal trends. The activity series ranks the relative reactivity of metals. It allows us to predict if certain chemicals will undergo single displacement reactions when mixed: metals near the top are most reactive and will displace metals near the bottom. Q: Which of these will react? 2Fe + 3CuSO4  Ni + NaCl  2Li + ZnCO3  2Al + 3 CuCl2  2Cu + Fe2(SO4)3 NR (no reaction) Zn + Li2CO3 Cu + 2AlCl3

  25. cold H2O H is the only nonmetal listed. H2 may be displaced from acids or can be given off when a metal reacts with H2O (producing H2 + metal hydroxide). The reaction with H2O depends on metal reactivity & water temp. Q: Will Mg react with H2O? hot H2O steam A: No for cold, yes if it is hot/steam Mg + H2O  H2 + Mg(OH)2 acid Q: Zn + HCl  H2 + ZnCl2 Complete these reactions: 2Al + 6H2O(steam)  Cu + H2O  Ca + H2SO4  2Na+ 2H2O  3H2+ 2Al(OH)3 NR H2 + CaSO4 H2 + 2NaOH

  26. 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.

  27. Reactivity of halogens Certain nonmetals, the halogens, also behave like this. The order of “strength” of the halogens is F2 Cl2 Br2 I2 Example: F2+ CuCl2  Cl2+ CuF2 I2+ CuCl2  Decreasing strength ↓ No RXN!!!

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

  29. 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: AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq) • Another example: 2 KMn04 + Na2C2O4 2 NaMnO4 + K2C2O4

  30. Special double displacement reactions to know: In these special DD reaction one of the two products decomposes. CaCO3 + 2 HCl CaCl2+ K2SO3+ 2HNO32KNO3+ NH4Cl + NaOHNaCl + H2CO3 CO2 + H2O SO2 + H2O H2SO3 NH4OH NH3 + H2O

  31. 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 + H2O • NaOH + HCl → NaCl + H2O • (NH4)2SO4 + 2H2O • 2NH4OH + H2SO4→

  32. LearningCheck Classify the following reactions as 1) single replacement 2) double replacement __A. 2Al + 3H2SO4 Al2(SO4)3 + 3H2 __B. Na2SO4 + 2AgNO3Ag2SO4 + 2NaNO3 __C. 3C + Fe2O3 2Fe + 3CO LecturePLUS Timberlake 99

  33. 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.164-168 & P. 172-177, • HW: Worksheets, P.169 # 1-7; P.204 # 3-6; P. 177 # 1-7,P. 197 # 1-7,P. 210 # 1-3

  34. Activity series lab • On the next slide, place a check in the corner of boxes where you think reactions will take place. • Get a plastic spot plate. • 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. • Write chemical equations for chemicals that reacted. Write NR where there was no reaction. • 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.

  35.   Mg + 2AgNO3  2Ag+ Mg(NO3)2 Cu + 2AgNO3  2Ag+ Cu(NO3)2 Zn + 2AgNO3  2Ag+ Zn(NO3)2 AgNO3   Mg + H2SO4  H2 + MgSO4 Zn + H2SO4  H2 + ZnSO4 H2SO4 NR   3Mg+ 2Fe(NO3)3  2Fe+ 3Mg(NO3)2 3Zn+ 2Fe(NO3)3  2Fe+ 3Zn(NO3)2 Fe(NO3)3 NR   Mg + CuCl2  Cu + MgCl2 Zn + CuCl2  Cu + ZnCl2 CuCl2 NR