1 / 34

Chemical Reactions

Chemical Reactions. State Standard. Standard 3- Interactions of Matter CLE 2- Analyze Chemical Reactions CLE 3- Explore Formulas and Equations CLE 4- Explain the Law of Conservation of Mass/Energy SPI 2 – identify reactants, products, and types of reactions

thaddeus-cortez
Download Presentation

Chemical Reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chemical Reactions

  2. State Standard Standard 3- Interactions of Matter CLE 2- Analyze Chemical Reactions CLE 3- Explore Formulas and Equations CLE 4- Explain the Law of Conservation of Mass/Energy SPI 2 – identify reactants, products, and types of reactions SPI 4 – balance chemical equations

  3. Chemical Equations • Chemical equations are used to represent chemical reactions • writing the equation doesn’t make it so! • Equations can be written with words or with formulas • You should be able to interpret a formula equation with words, as well as write the formula equation from words

  4. Substances initially present before reaction are called reactant(s) • Substances present after the reaction has occured are called product(s) • An arrow (→) separates the products and reactants

  5. Symbols and Phase Labels • Symbols and phase labels are used to indicate the physical state of the reactants and products and conditions under which the rxn occurs (s) = solid (l) = liquid (g) = gas (aq) = aqueous solution, dissolved in water ∆ / heat = heat added catalyst formula = catalyst temp/pressure = conditions of rxn

  6. Describe the following chemical equation in words: 2H2O + O2 2H2O2

  7. 2H2O + O2 2H2O2 Two molecules of water combine with one molecule of oxygen gas to form (yield) two molecules of hydrogen peroxide

  8. Write an equation for the following: Solid sodium metal combines with liquid water to yield aqueous sodium hydroxide and hydrogen gas.

  9. Na(s) + H2O(l) NaOH(aq) + H2(g)

  10. Write this equation: Solid sodium hydrogen carbonate and aqueous hydrochloric acid react in a beaker to produce aqueous sodium chloride, liquid water, and carbon dioxide gas.

  11. NaHCO3(s) + HCl(aq) NaCl(aq) + H2O(l) + CO2(g)

  12. Balancing Chemical Equations • Coefficients are used in front of reactants and products in a chemical equation to balance the equation according to the Law of Conservation of Mass, which must be obeyed in all chemical processes • Formulae of reactants and products are never changed in order to balance an equation

  13. Balancing Chemical Equations • How would you write an equation for making a bicycle? • Use these parts: frame (F) wheels (W) pedals(P) handlebars (H)

  14. Bicycle F + 2W + 2P + H  FW2P2H One frame, two wheels, two pedals, and one set of handlebars yields one bicycle (an FW2P2H)

  15. Steps in Balancing An Equation Fe3O4 + H2 Fe +H2O Fe:Fe3O4 + H23 Fe +H2O O:Fe3O4 + H2 3 Fe +4H2O H: Fe3O4 + 4 H2 3 Fe +4H2O

  16. Balance these equations • H2 + O2 H2O • AgNO3 + H2S  Ag2S + HNO3 • Zn(OH)2 + H3PO4  Zn3(PO4)2 + H2O

  17. Balance these equations • 2H2 + O2 2H2O • 2AgNO3 + H2S  Ag2S + 2HNO3 • 3Zn(OH)2 + 2H3PO4  Zn3(PO4)2 +6H2O

  18. Types of Reactions • There are 5 major classes of reactions: synthesis decomposition combustion single replacement/displacement double replacement/displacement • Classifying a reaction is often helpful in predicting products

  19. How to Classify a Reaction • Look at reactants and products… Synthesis: 2 or more substances combining to make 1 substance: 2 → 1 Decomposition: 1 substance breaking down into 2 or more substances: 1 → 2 Combustion: reaction with elemental O2 - we will only consider 1 type- hydrocarbon combustion - complete combustion produces CO2 and H2O always, regardless of hydrocarbon

  20. Double Replacement: ionic*cmpd1 + ionic cmpd2 → ionic cmpd3 + ionic cmpd4 -*May involve acids and water, as well Single Replacement: element + cmpd → element + cmpd

  21. Types of Reactions and Predicting Products

  22. State Standard Standard 3- Interactions of Matter CLE 2- Analyze Chemical Reactions CLE 3- Explore Formulas and Equations CLE 4- Explain the Law of Conservation of Mass/Energy SPI 2 – identify reactants, products, and types of reactions SPI 3- predict products of reactions SPI 4 – balance chemical equations

  23. Synthesis Reactions • Two or more substances react to form a single new substance. • Reactants may be 2 elements or an element and a compound 2K(s) + Cl2(g) 2KCl(s) • Cmpd formed may be molecular or ionic • Follow rules for writing formulas of ionic cmpds • Give a reasonable formula for a molecular cmpd

  24. Decomposition Reaction • A single compound breaks down into two or more simpler products. • Products may be 2 elements or an element and compound or 2 compounds 2HgO(s) 2Hg(l) + O2(g) • Most elements exist in elemental form as a monatomic atom • Exceptions: H2, N2, O2, F2, Cl2, Br2, I2, P4 and S8

  25. Decomposition Products • Carbonates (compounds containing CO32–) give off carbon dioxide and leave oxide compounds behind. Sulfates (with SO42–) give off sulfur trioxide and leave oxide compounds behind.Hydroxides (with OH1–) produce water and leave oxide compounds behind.Chlorates (with ClO31–) give off oxygen and leave chloride compounds behind.Hydrates (with H2O) break up into water and anhydrous compounds.Binary compounds (made of just two elements) break down into their elements. (Don't forget about HOFBrINClSP!)

  26. Combustion Reactions • Burning reaction • An element or compound (hydrocarbon) reacts with oxygen (O2) and often produces heat and light. • CO2 and H2O are always the products of complete hydrocarbon combustion. • Incomplete combustion produces CO, rather than CO2 C8H18(l)+ O2(g) CO2(g)+H2O(l)

  27. 3 types *The activity series must be used to determine products for all types of SR rxns 1) A single metal displaces another metal from a compound to produce a new compound and a new single metal. Fe(s) + Pb(NO3)2(aq)  Fe(NO3)2(aq) + Pb(s) A metal can replace any metal below it on the activity series Fe is above Pb on the activity series, so it can displacePb from the compound Nitrates are insoluble, so aq Single Replacement Reactions

  28. 2) A metal displaces H from water or acid* * be sure to read conditions for these a) Pb(s) + H2O(l) → ? (NR) - Pb displaces H from acids only, so this one is NR b) Cr(s) + H2O(l) → ? (NR) - Cr displaces H from steam- rxn doesn’t say temp. is above room temp., so no steam and NR 3) A halogen displaces another halogen from a compound -Halogens go in same order as group: F (most reactive) → I (least reactive) a) Br2+ NaCl→ ? (NR) • Br is below Cl, so NR b) F2 + CaBr2 → ? (Br2 + CaF2) - F is above Br, so Br2 + CaF2

  29. Double Replacement Reactions • Cations and anions in 2 ionic compounds switch partners: inner 2 and outer 2- 3Ba(NO3)2 + 2H3PO4 Ba3(PO4)2 + 6HNO3 • Subscripts do NOT carry from reactant side to product side- they are there to balance the ions in the formula to get the correct formula • Cation always first in formula!! • Order of product compounds doesn’t matter- either compound can come first

  30. DR Reactions • DR reactions have conditions under which they will not occur… • There must be a driving force to make the reaction proceed otherwise there is no rxn-NR • Driving forces include: evolution of gas formation of a precipitate-solid formation of a liquid (H2O only liquid we use) formation of a WA/WB (not in this class)

  31. Gas forming reactions must be learned • H2S(g),NH3(g), CO2(g), and SO2(g) are most common, but are hard to recognize as products… • NH4OH(aq) = NH3(g)+ H2O(l) • H2CO3(aq) = CO2(g) + H2O(l) • H2SO3(aq) = SO2(g)+ H2O(l) • Liquid forming , i.e. water, reactions are called acid- base reactions • Reaction of an acid (H-) with a base (-OH) will produce water and a salt (ionic compound) HCl(aq) + NaOH(aq) → H2O(l) + NaCl(aq)

  32. Cont’d… • Precipitate reactions require the use of a solubility table (handout) to determine if a compound is aqueous in water (soluble) or will precipitate out (insoluble) 3Ba(NO3)2(aq) + 2H3PO4(aq)  Ba3(PO4)2(?) + 6HNO3(?) • You must check the products- no gas or liquid formed, so check solubility table for solid formation… • Generally check the anion- few rules involve cations • Phosphates- frequently insoluble → solids • Nitrates- generally soluble → aqueous 3Ba(NO3)2(aq) + 2H3PO4(aq)  Ba3(PO4)2(s) + 6HNO3(aq)

  33. Net Ionic Equations • Show only the ions participating in the reaction • The ions that do not participate are called spectator ions • Steps: • All (aq) compounds are broken apart into their respective ions; this is a better representation of aq compounds • Solids, liquids and gases are not broken apart • Ions that appear on both the reactant and product side are cancelled; these are the spectator ions • Coeff must match in order to cancel ions

  34. Example: Ba(NO3)2(aq) + (NH4)2S(aq) → 2NH4NO3(aq) + BaS(s) Ba2+(aq) + 2NO3-(aq) + 2NH4+(aq) + S2-(aq) → 2NH4+(aq) + 2NO3-(aq) + BaS(s) Ba2+(aq) +S2-(aq) → BaS(s)

More Related