chemtest2 - - rate = concentration/ time -...

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- rate = concentration/ time - C=C final -C initial - concentration units: mol/L (M) - rate units: mol/Lxtime - general rate expression: rate = aA + bB  cC + dD rate = -1/a [A]/ t = -1/b [B]/ t = 1/c [C]/ t = 1/d [D]/ t - iodine clock reaction H 2 O 2 (aq) + 2I - (aq) + 2H 3 O + (aq) 4H 2 O (l) + I 2 (aq) as soon as I 2 is formed, vitamin C rapidly reduces it to I - 2 H 2 O (l) + I 2 (aq) + C 6 H 8 O 6 (aq) C 6 H 6 O 6 (aq) + 2H 3 O + (aq) + 2I - (aq) - when solution is less concentrated, takes longer to change color - when solution is hotter, changes color more quickly - catalysts: accelerate reactions but are not consumed themselves - rate of rxn = k[A] m [B] n - if a homogeneous catalytic species is present, may be included in rate eq but not in balanced - determining initial rate: [products]/ time or - [reactants]/ time - [R] t /[R] 0 = fraction remaining zero order first order second order [R] 0 –[R] t = kt ln([R] t /[R] 0 ) = -kt 1/[R] t – 1/[R] 0 = kt [R] t = -kt + [R] 0 ln [R] t = -kt + [R] 0 1/[R] t = +kt + 1/[R] 0 y = mx + b y = mx + b y = mx + b ****table 15.1 pg 689**** - half life – time req for the concentration of a reactant to decrease ½ initial - longer half life, slower the rxn - first order: t 1/2 = 0.693/k - zero order: t 1/2 = [R] 0 /2k - second order: t 1/2 = 1/k[R] 0 - collision theory of rxn rates - reacting molecules must collide with one another
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This note was uploaded on 02/29/2012 for the course CHEMISTRY 104 taught by Professor Fredrickson during the Spring '11 term at Wisconsin.

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chemtest2 - - rate = concentration/ time -...

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