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Chemical Reactions


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Chemical Reactions

  1. 1. 1. Reactants = the substances you start with 2. Products = the substances you end up with∞∞
  2. 2. - Page 321ProductsReactants
  3. 3. •The way atoms are joined is changedAtoms aren’t created or destroyed.
  4. 4. ∞the arrow (→) separates the reactantsfrom the products (arrow points to products) ∞Read as: “reacts to form” or yields∞ The plus sign = “and”
  5. 5. ∞(s) after the formula = solid: Fe(s)∞ (g) after the formula = gas: CO2(g)∞ (l) after the formula = liquid: H2O(l) ∞(aq) after the formula = dissolved in water, an aqueoussolution: NaCl(aq) is a salt water solution.
  6. 6. ∞ indicates a reversible reaction.∞ shows that heat is supplied to the reaction.∞ , or is used to indicate a catalyst used supplied, in this case, platinum.∞ , indicates a pressure other than STP.
  7. 7. ∞used after a productindicates a gas has been produced: H2↑ ∞ used after a productindicates a solid has been produced: PbI2↓
  8. 8. Summary of Symbols
  9. 9. What is a Catalyst?• A substance that speeds up areaction without being changed by the reaction. • Enzymes are biological or protein catalysts.
  10. 10. . Exothermic - reactions that releaseenergy to their surroundings (usually in the form of heat) Endothermic - reactions that need toabsorb heat from their surroundings to proceed.
  11. 11. • Spontaneous Reactions - Reactions that proceed immediately when two substances are mixed together. Not all reactions proceed spontaneously.• Activation Energy – the amount of energy that is required to start a chemical reaction.• Once activation energy is reached the reaction continues until you run out of material to react.
  12. 12. • Uses formulas and symbols to describe a reaction • doesn’t indicate how many. • All chemical equations are sentences that describe reactions.
  13. 13. ∞There are 8 elements that never want to be alone.∞They form diatomic molecules.∞H2 , N2 , O2 , F2 , Cl2 , Br2 , I2 , and At2 ∞The –ogens and the –ines ∞1 + 7 pattern on the periodic table
  14. 14. Solid iron reacts with oxygen gas to form solid iron oxide (rust).
  15. 15. A silver spoon tarnishes. The solid silverreacts with sulfur in the air to make solid silver sulfide, the black material we call tarnish.
  16. 16. ∞Also called combination reactions. ∞2 elements, or compoundscombine to make one compound. ∞A + B AB∞Na (s) + Cl2 (g) NaCl (s) ∞Ca (s) +O2 (g) CaO (s)
  17. 17. ∞SO3(s) + H2O(l) H2SO4 (s) ∞We can predict the products if they are two elements.∞Mg (s) + N2 (g) Mg3N2 (s)
  18. 18. ∞ Additional Important Notes: a) Some nonmetal oxides react with water to produce an acid: SO2 + H2O  H2SO3 (This is what happens to make “acid rain”) b) Some metallic oxides react with water to produce a base: CaO + H2O  Ca(OH)2
  19. 19. ∞decompose = fall apart∞one compound (reactant) falls apart into two or more elements or compounds. ∞Usually requires energy ∞AB A + B electricity ∞NaCl Na + Cl2 ∞CaCO3 CaO + CO2
  20. 20. ∞Can predict the products if it is a binary compound (made up of only two elements)∞Falls apart into its elements∞H2O electricity H2 (g) + O2 (g)∞HgO Hg (s) + O2 (g)
  21. 21. ∞If the compound has more than two elements you must be given one of the products ∞The other product will be from the missing pieces∞NiCO3 (aq) CO2 (g)+ Ni (s)∞H2CO3(aq) H2 (g)+ CO2 (g)
  22. 22. ∞Also referred to as single displacement∞ One element replaces another∞Reactants must be an element and a compound.∞Products will be a different element and a different compound.
  23. 23. ∞ Na + KCl K + NaCl (Cations switched)∞ F2 + LiCl LiF + Cl2 (Anions switched)
  24. 24. ∞A+BC AC+B∞2Na + SrCl2 Sr + 2NaCl∞F2 + LiCl LiF + Cl2
  25. 25. ∞We can tell a reaction will happen∞Some are more active than other∞More active replaces less active
  26. 26. The “Activity Series” of MetalsHigher Lithiumactivity Potassium 1) Metals can replace other Calcium Sodium metals, provided they are Magnesium above the metal they are Aluminum Zinc trying to replace Chromium (for example, zinc will replace lead) Iron Nickel 2) Metals above hydrogen can Lead Hydrogen replace hydrogen in acids. Bismuth Copper Mercury 3) Metals from sodium upward SilverLower Platinum can replace hydrogen inactivity Gold water.
  27. 27. The “Activity Series” of HalogensHigher Activity Halogens can replace other Fluorine halogens in compounds, Chlorine Bromine provided they are above the Iodine halogen they are trying toLower Activity replace. 2NaCl(s) + F2(g)  ??? 2NaF(s) + Cl2(g) MgCl2(s) + Br2(g)  ??? No Reaction!
  28. 28. ∞Two things replace each other. ∞Reactants must be two ionic compounds or acids.∞Usually in aqueous solution ∞ AB+CD AD+CB
  29. 29. ∞ZnS + 2HCl ZnCl + H2SAgNO3 + NaCl∞ AgCl + NaNO3
  30. 30. ∞ NaOH + FeCl3 -The positive ions change place.∞NaOH + FeCl3 Fe+3 OH- + Na+1 Cl-1= NaOH + FeCl3 Fe(OH)3 + NaCl
  31. 31. ∞Have certain “driving forces”, or reasons -Will only happen if one of the products: a) doesn’t dissolve in water and forms a solid (a “precipitate”), or b) is a gas that bubbles out, orc) is a molecular compound (which will usually be water).
  32. 32. ∞Combustion means “add oxygen”∞Normally, a compound composed of only C, H, (and maybe O) is reacted with oxygen – usually called “burning” ∞If the combustion is complete, the products will be CO2 and H2O.∞If the combustion is incomplete, the products will be CO (or possibly just C) and H2O.
  33. 33. ∞A reaction in which a compound (often carbon) reacts with oxygen ∞ CH4 + O2 CO2 + H2O ∞ C3H8 + O2 CO2 + H2O ∞ C6H12O6 + O2 CO2 + H2O
  34. 34. The charcoal used in a grill is basically carbon.The carbon reacts with oxygen to yield carbon dioxide. Thechemical equation for this reaction is C + O2  CO2
  35. 35. ∞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 NH4OH + H2SO4 → (NH4)2SO4 + H2O
  36. 36. ∞ H2 + O2 Synthesis ∞H2O Decomposition∞ AgNO3 + NaCl Double replacement ∞ Zn + H2SO4 Single replacement ∞ HgO Decomposition ∞ KBr +Cl2 Single replacement∞ Mg(OH)2 + H2SO3 Double replacement
  37. 37. ∞ HNO3 + KOH Acid/Base ∞ CaPO4 Decomposition ∞ AgBr + Cl2 Single replacement ∞ Zn + O2 Synthesis ∞ HgO + Pb Single replacement ∞ HBr + NH4OH Acid/Base∞ Cu(OH)2 + KClO3 Double replacement
  38. 38. An equation: ∞Describes a reaction ∞Must be balanced because to follow Law of Conservation of Energy∞Can only be balanced by changing the coefficients.∞Has special symbols to indicate state, and if catalyst or energy is required. ∞Can describe 5 different types of reactions.