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Chapter 12 - 1 CHEMICAL KINETICS Study which examines how...

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1 CHEMICAL KINETICS - Study which examines how fast chemical reactions occur and why? NaOH (aq) + HCl (aq) NaCl (aq) + H 2 O (l) - Neutralization happens very fast. 2 Fe (s) + 3 O 2 (g) 2 Fe 2 O 3 (s) - Rusting of iron happens very slow. Reaction rate – speed of a reaction – n (Greek nu) Consider a simple reaction A B ( 29 ( 29 ( 29 ( 29 ν = - - = moles of B final moles of B initial time final time initial molesof B t - higher reaction rate means - more moles of B are formed in a set time - a set number of moles of B forms quicker. As moles of B increases, moles of A decrease. = - ν molesofA t In a constant volume container, the rate can also be defined as the change in concentration of the product divided by the change in time. ν = [ ] B t FACTORS WHICH AFFECT REACTION RATE 1. Concentration of reactants - Reaction with higher amount of starting material will usually proceed faster. 2. Temperature of reaction - Higher temperature usually increases reaction rate. 3. Catalysis - Catalyst is a substance that speeds up a reaction, yet it remains unchanged. - Catalysts are very important in industry. - “Time is money.” - Enzymes are biochemical catalysts. 4. Surface Area - A fine powder reacts quicker than a big crystal.
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2 REACTION RATES Measuring reaction rate - measure concentration of reactant as it reacts to form product Example: C 4 H 9 Cl (aq) + H 2 O (l) C 4 H 9 OH (aq) + HCl (aq) Overhead: Table of [C 4 H 9 Cl] and time Overhead: Graph of [C 4 H 9 OH] vs. time Instantaneous rate: - slope of concentration versus time plot
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