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Exploring Chemical Reactions: Types & Principles

Discover evidence of chemical reactions, from color changes to formation of gases and solids. Learn the principles, balancing equations, elements, and types of reactions. Perfect for understanding synthesis, decomposition, combustion, and more.

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Exploring Chemical Reactions: Types & Principles

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  1. Unit 6 Chemical Reactions: An Introduction

  2. Evidence of a Chemical Reaction • Color change • Temperature change • Formation of a gas (bubbles) • Formation of a precipitate (a solid forming when 2 solutions are mixed together)

  3. Principles of Chemical Reactions: • A chemical equation tells you what reactant chemicals are used and what product chemicals are formed. • A chemical equation does not tell you how long the chemical reaction will take, how to mix the chemicals, or at what temperature.

  4. 2 H2 + 1 O22 H2O • The numbers in front of the chemicals, the coefficient, tell you the number of atoms and molecules involved, or the number of moles involved. 2 molecules of hydrogen are added to 1 molecule of oxygen makes (yields) 2 molecules of water. 2 moles of hydrogen are added to 1 mole of oxygen makes (yields) 2 moles of water.

  5. Law of Conservation of Mass • You can not destroy or create substances in a chemical reaction. You simply change how they appear. • Mass at beginning = Mass at end of of reaction reaction

  6. To balance equations: • a. Know what the reactants and products are • A + B  C + D • reactants products • Know the correct formula for each substance • c. Conserve atoms by placing coefficients in front of the chemicals so that you have the same number of atoms of each element on opposite sides of } }

  7. Notation of phase may be used. s = solid L = liquid g = gas aq = aqueous (dissolved in water) Zn(s) + 2 HCl(aq) ZnCl2 (aq) + H2 (g)

  8. Balancing equations using molecule model kits: H2 + O2  H2O

  9. Element colors Hydrogen – Yellow Carbon – Black Nitrogen – Blue Oxygen – Red Chlorine - Green

  10. Types of Chemical Reactions Synthesis X + Y  XY Decomposition XY  X + Y Combustion CxHyYz + O2 CO2 + H2O Single Replacement A + XY  AY + X Double Replacement AB + XY  AY + XB

  11. Types of chemical reactions: • Synthesis (or combination): combining 2 or more small molecules or atoms into one larger molecule Synthesis X + Y  XY H2(g) + O2(g) H2O (g)

  12. Decomposition: breaking a large molecule into 2 or more smaller molecules or atoms Decomposition XY  X + Y (NH4)2Cr2O7(s)  N2(g) + H2O (g) + Cr2O3(s) Combustion: a hydrocarbon molecule combining with oxygen to make CO2 and H2O Combustion CxHyYz + O2 CO2 + H2O C2H6O (g) + O2(g) CO2(g) + H2O (g)

  13. Single replacement: an element exchanges places with another element in a compound to make a new element and a new compound Single Replacement A + XY  AY + X AgNO3(aq) + Cu (s) Cu(NO3)2(aq) + Ag (s) Double replacement: when 2 compounds exchange partners to make 2 new compounds Double Replacement AB + XY  AY + XB FeCl3(aq) + NaOH (aq) Fe(OH)3(s) + NaCl (aq)

  14. Writing balanced ionic equations for chemicals dissolving in H2O NaCl (s) NH4Cl (s)  CaCl2 (s)  (NH4)2CO3 (s) 

  15. AgNO3 (s) CuCl2 (s)  NaHCO3 (s)  Na2SO4 (s) 

  16. Types of Chemical Reactions Synthesis X + Y  XY Decomposition XY  X + Y Combustion CxHyYz + O2 CO2 + H2O Single Replacement A + XY  AY + X Double Replacement AB + XY  AY + XB

  17. .50 mol 1.00 mol Fe2O3 + C  Fe + CO 2 ____g 12.01g ____g ____g

  18. Some reactions give off energy. These are called exothermic chemical reactions. CaO (s) + H2O (L)  Ca(OH)2(s) Some reactions absorb energy. These are called endothermic chemical reactions. Ba(OH)2.8H2O(s) + NH4NO3(s) Ba(NO3)2(aq) + NH3(g) +H2O(L) Some chemical reactions are reversible. 2 H2(g) + O2(g) 2 H2O (g) + energy energy + 2 H2O (L)  2 H2(g) + O2 (g)

  19. Review 1. 2C3H8O + 9O2 6CO2 + 8H2O 2H2O2 2H2O + O2 3C + 2Fe2O3 3CO2 + 4 Fe 6CO2 + 6H2O  C6H12O6 + 6 O2 2NaCl + Pb(NO3)2 PbCl2 + 2 NaNO3 2 H2 + O2 2 H2O 2. Synthesis – f, decoposition – b, single replacement – c, double replacement – e, combustion – a (d doesn’t fit any of these) 3. 4Fe + 3 O2 2 Fe2O3 4. Ba(NO3)2 Ba+2 + 2 NO3-1 AlCl3 Al+3 + 3 Cl-1 (NH4)3PO4 3NH4+1 + PO4-3 5. .20 mol .40 mol CaCO3 + 2HCl  CaCl2 + H2CO3 20.02g 14.58g 22.20g 12.40g

  20. Use on the exam: • Periodic Table • Formula sheet • Mole Wheel • Common Ions • Calculator • Blank Periodic Table (you wrote on)

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