or O.I.L.) Reduction is the gain of electrons (G.E.R. Corrosion protection Recognizing Redox Reactions Oxidation is the loss of electrons (L.E.O. Balancing redox reactions: skeleton & half-reaction method 3. Exothermic Reactionģ ELECTROCHEMISTRY SUMMARY Skills to Master 1. Catalysts decrease time to reach equilibrium but do not change K c or equilibrium position. Catalysts provide an alternative reaction pathway with a lower activation energy. The activation energy is the minimum amount of collision energy required to force both reactant molecules together into a single entity called an activated complex. This is the minimum amount of energy required to cause a chemical reaction to occur. Endothermic Reaction Activation Energy An energy barrier between reactants and products. Combustion reactions in open systems produce H 2 O(g), while in closed systems H 2 O(l) is produced. Calorimetry n rh=mc t where: n = moles of chemical specified (mol) calculated either by n=cv for solutions or n=m/m for solids r H = molar enthalpy of reaction (KJ/mol) m = total (volume) mass of water in calorimeter (Kg) c = 4.19 KJ/Kg o C t = temperature change ( o C) t i t f Standard Enthalpies of Formation Used to calculate enthalpy change for a chemical reaction Where: H = enthalpy change kj Σ means sum of n = moles (mol) r H = molar enthalpy of formation (kj/mol) from data book pages 6 & 7 *Notes: r H of elements in their natural state is 0 kj/mol. r for general reaction, c for combustion, f for formation. or r H = molar enthalpy of reaction for specified chemical (kj/mol) Subscripts can be used to denote the reaction type: e.g. given in problem as moles of chemical statement. 2 THERMOCHEMISTRY SUMMARY SKILLS TO MASTER Carrying out calorimetry calculations Relating enthalpy & molar enthalpy calculations Using standard enthalpies of formation Activation energy FORMULAS MUST BE MEMORIZED Enthalpy change Hn r H H = enthalpy change (kj) n = amount of substance (moles), from either: - the balancing number from the equation.
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