Lec9 - Lecture 9: Chemical Reactions and Lecture 9:...

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1 Lecture 9: Chemical Reactions and Stoichiometry 2 Reactants Reactants Products Products C 6 H 12 O 6 (aq) 2 C 2 H 5 OH( l ) + 2 CO 2 (g) glucose ethanol carbon dioxide yeast Conditions may be shown over the arrow. e.g. heat ( Δ ) reflux catalyst present (yeast) Physical states are often listed: (g) gas (s) solid ( l ) liquid (aq) aqueous (dissolved in water) Chemical Equations
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3 O 2 molar mass Balanced equations Balanced equations obey the law of conservation of mass (Lavoisier 1789). 2 C 2 H 6 (g) + 7 O 2 (g) 4 CO 2 (g) + 6 H 2 O( l ) Nanoscale Nanoscale 2 molecules 7 molecules 4 molecules 6 molecules Macroscale 2 moles 7 moles 4 moles 6 moles 2(30.0)= 60.0 g 7(32.0)= 224.0 g 4(44.0)= 176.0 g 6(18.0)= 108.0 g C 2 H 6 molar mass 284.0 g 284.0 g “Mass is neither created nor destroyed in a chemical reaction.” Chemical Equations 4 Stoichiometry Stoichiometry The relationship between the number of reactant and product molecules in a chemical equation. CaCO 3 (s) + 2 HNO 3 (aq) Ca(NO 3 ) 2 (aq) + CO 2 (g) + H 2 O( l ) A stoichiometric coefficient Chemical Equations
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5 Types of reactions 6 Combination Reactions + XZ X Z Element plus halogen or O 2 : 2 Mg(s) + O 2 (g) 2 MgO(s) I 2 (s) + Zn(s) ZnI 2 (s) There are other types: 2 SO 2 (g) + O 2 (g) 2 SO 3 (g)
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7 + XZ X Z Occasionally by shock: 4 C 3 H 5 (NO 3 ) 3 ( l ) 12 CO 2 (g) + 10 H 2 O( l ) + 6 N 2 (g) + O 2 (g) Often initiated by heat: CaCO 3 (s) CaO(s) + CO 2 (g) 2 KNO 3 (s) 2 KNO 2 (s) + O 2 (g) heat 800 - 1000°C Decomposition Reactions 8 Displacement Reactions Some other examples: F 2 (g) + 2 LiC l (s) 2 LiF(s) + C l 2 (g) Some metals displace another metal from its salt Fe(s) + CuSO 4 (aq) FeSO 4 (aq) + Cu(s) ++ A XZ AZ X Zn(s) + 2 AgNO 3 (aq) Zn(NO 3 ) 2 (aq) + 2 Ag(s) 2 Na(s) + 2 H 2 O( l ) 2 NaOH(aq) + H 2 (g)
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9 Exchange Reactions ++ AD XZ AZ XD
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Lec9 - Lecture 9: Chemical Reactions and Lecture 9:...

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