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Page 1 RATE/VELOCITY OF CHEMICAL REACTION : Rate = t c ? ? = sec . lit / mol = mol lit ?1 time ?1 = mol dm ?3 time ?1 Types of Rates of chemical reaction : For a reaction R ?? ? P Average rate = taken time Total ion concentrat in change Total R instantaneous = 0 t lim ? ? ? ? ? ? ? ? ? t c = dt dc = ? dt ] R [ d = dt ] P [ d RATE LAW (DEPENDENCE OF RATE ON CONCENTRATION OF REACTANTS) : Rate = K (conc.) order ? differential rate equation or rate expression Where K = Rate constant = specific reaction rate = rate of reaction when concentration is unity unit of K = (conc) 1? order time ?1 Order of reaction : m 1 A + m 2 B ?? products. R ? [A] P [B] q Where p may or may not be equal to m 1 & similarly q may or may not be equal to m 2 . p is order of reaction with respect to reactant A and q is order of reaction with respect to reactant B and (p + q) is overall order of the reaction. Page 2 RATE/VELOCITY OF CHEMICAL REACTION : Rate = t c ? ? = sec . lit / mol = mol lit ?1 time ?1 = mol dm ?3 time ?1 Types of Rates of chemical reaction : For a reaction R ?? ? P Average rate = taken time Total ion concentrat in change Total R instantaneous = 0 t lim ? ? ? ? ? ? ? ? ? t c = dt dc = ? dt ] R [ d = dt ] P [ d RATE LAW (DEPENDENCE OF RATE ON CONCENTRATION OF REACTANTS) : Rate = K (conc.) order ? differential rate equation or rate expression Where K = Rate constant = specific reaction rate = rate of reaction when concentration is unity unit of K = (conc) 1? order time ?1 Order of reaction : m 1 A + m 2 B ?? products. R ? [A] P [B] q Where p may or may not be equal to m 1 & similarly q may or may not be equal to m 2 . p is order of reaction with respect to reactant A and q is order of reaction with respect to reactant B and (p + q) is overall order of the reaction. INTEGRATED RATE LAWS : C 0 or 'a' is initial concentration and C t or a ? x is concentration at time 't' (a) zero order reactions : Rate = k [conc.]º = constant Rate = k = ' t ' C C t 0 ? or C t = C 0 ? kt Unit of K = mol lit ?1 sec ?1 , Time for completion = k C 0 at t 1/2 , C t = 2 C 0 , so kt 1/2 = 2 C 0 ? t 1/2 = k 2 C 0 ? t 1/2 ? C 0 (b) First Order Reactions : (i) Let a 1 st order reaction is, A ?? ? Products t = k 303 . 2 log x a a ? or k = t 303 . 2 log t 0 C C ? t 1/2 = k 2 n ? = k 0.693 = Independent of initial concentration. t Avg. = k 1 = 1.44 t 1/2 . Graphical Representation : t = k 303 . 2 ? log C t + 2.303 k log C 0 ? log C /C or log a/ax 0 t 't' tan = 2.303 ? k 't' tan = ? 2.303 k ? log C t (c) Second order reaction : 2 nd order Reactions Two types A + A ?? products A + B ?? products. a a a b 0 (a ? x) (a ?x) a ? x b ? x ? dt dx = k (a?x) 2 dt dx = k (a ? x) (b ? x) ? ) x a ( 1 ? ? a 1 = kt k = ) b a ( t 303 . 2 ? log ) x b ( a ) x a ( b ? ? Page 3 RATE/VELOCITY OF CHEMICAL REACTION : Rate = t c ? ? = sec . lit / mol = mol lit ?1 time ?1 = mol dm ?3 time ?1 Types of Rates of chemical reaction : For a reaction R ?? ? P Average rate = taken time Total ion concentrat in change Total R instantaneous = 0 t lim ? ? ? ? ? ? ? ? ? t c = dt dc = ? dt ] R [ d = dt ] P [ d RATE LAW (DEPENDENCE OF RATE ON CONCENTRATION OF REACTANTS) : Rate = K (conc.) order ? differential rate equation or rate expression Where K = Rate constant = specific reaction rate = rate of reaction when concentration is unity unit of K = (conc) 1? order time ?1 Order of reaction : m 1 A + m 2 B ?? products. R ? [A] P [B] q Where p may or may not be equal to m 1 & similarly q may or may not be equal to m 2 . p is order of reaction with respect to reactant A and q is order of reaction with respect to reactant B and (p + q) is overall order of the reaction. INTEGRATED RATE LAWS : C 0 or 'a' is initial concentration and C t or a ? x is concentration at time 't' (a) zero order reactions : Rate = k [conc.]º = constant Rate = k = ' t ' C C t 0 ? or C t = C 0 ? kt Unit of K = mol lit ?1 sec ?1 , Time for completion = k C 0 at t 1/2 , C t = 2 C 0 , so kt 1/2 = 2 C 0 ? t 1/2 = k 2 C 0 ? t 1/2 ? C 0 (b) First Order Reactions : (i) Let a 1 st order reaction is, A ?? ? Products t = k 303 . 2 log x a a ? or k = t 303 . 2 log t 0 C C ? t 1/2 = k 2 n ? = k 0.693 = Independent of initial concentration. t Avg. = k 1 = 1.44 t 1/2 . Graphical Representation : t = k 303 . 2 ? log C t + 2.303 k log C 0 ? log C /C or log a/ax 0 t 't' tan = 2.303 ? k 't' tan = ? 2.303 k ? log C t (c) Second order reaction : 2 nd order Reactions Two types A + A ?? products A + B ?? products. a a a b 0 (a ? x) (a ?x) a ? x b ? x ? dt dx = k (a?x) 2 dt dx = k (a ? x) (b ? x) ? ) x a ( 1 ? ? a 1 = kt k = ) b a ( t 303 . 2 ? log ) x b ( a ) x a ( b ? ? METHODS TO DETERMINE ORDER OF A REACTION (a) Initial rate method : r = k [A] a [B] b [C] c if [B] = constant [C] = constant then for two different initial concentrations of A we have 1 0 r = k [A 0 ] 1 a , 2 0 r = k [A 0 ] 2 a ? a 2 0 1 0 0 0 ] A [ ] A [ r r 2 1 ? ? ? ? ? ? ? ? ? (b) Using integrated rate law : It is method of trial and error. (c) Method of half lives : for n th order reaction t 1/2 ? 1 n 0 ] R [ 1 ? (d) Ostwald Isolation Method : rate = k [A] a [B] b [C] c = k 0 [A] a METHODS TO MONITOR THE PROGRESS OF THE REACTION : (a) Progress of gaseous reaction can be monitored by measuring total pressure at a fixed volume & temperature or by measuring total volume of mixture under constant pressure and temperature. ? k = t 2.303 log t 0 0 P nP 1) (n P ? ? {Formula is not applicable when n = 1, the value of n can be fractional also.} (b) By titration method : 1. ? a ? V 0 a ? x ? V t ? k = t 2.303 log t 0 V V 2. Study of acid hydrolysis of an easter. k = t 303 . 2 log t 0 V V V V ? ? ? ? (c) By measuring optical rotation produced by the reaction mixture : k = t 303 . 2 log ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? t 0 Page 4 RATE/VELOCITY OF CHEMICAL REACTION : Rate = t c ? ? = sec . lit / mol = mol lit ?1 time ?1 = mol dm ?3 time ?1 Types of Rates of chemical reaction : For a reaction R ?? ? P Average rate = taken time Total ion concentrat in change Total R instantaneous = 0 t lim ? ? ? ? ? ? ? ? ? t c = dt dc = ? dt ] R [ d = dt ] P [ d RATE LAW (DEPENDENCE OF RATE ON CONCENTRATION OF REACTANTS) : Rate = K (conc.) order ? differential rate equation or rate expression Where K = Rate constant = specific reaction rate = rate of reaction when concentration is unity unit of K = (conc) 1? order time ?1 Order of reaction : m 1 A + m 2 B ?? products. R ? [A] P [B] q Where p may or may not be equal to m 1 & similarly q may or may not be equal to m 2 . p is order of reaction with respect to reactant A and q is order of reaction with respect to reactant B and (p + q) is overall order of the reaction. INTEGRATED RATE LAWS : C 0 or 'a' is initial concentration and C t or a ? x is concentration at time 't' (a) zero order reactions : Rate = k [conc.]º = constant Rate = k = ' t ' C C t 0 ? or C t = C 0 ? kt Unit of K = mol lit ?1 sec ?1 , Time for completion = k C 0 at t 1/2 , C t = 2 C 0 , so kt 1/2 = 2 C 0 ? t 1/2 = k 2 C 0 ? t 1/2 ? C 0 (b) First Order Reactions : (i) Let a 1 st order reaction is, A ?? ? Products t = k 303 . 2 log x a a ? or k = t 303 . 2 log t 0 C C ? t 1/2 = k 2 n ? = k 0.693 = Independent of initial concentration. t Avg. = k 1 = 1.44 t 1/2 . Graphical Representation : t = k 303 . 2 ? log C t + 2.303 k log C 0 ? log C /C or log a/ax 0 t 't' tan = 2.303 ? k 't' tan = ? 2.303 k ? log C t (c) Second order reaction : 2 nd order Reactions Two types A + A ?? products A + B ?? products. a a a b 0 (a ? x) (a ?x) a ? x b ? x ? dt dx = k (a?x) 2 dt dx = k (a ? x) (b ? x) ? ) x a ( 1 ? ? a 1 = kt k = ) b a ( t 303 . 2 ? log ) x b ( a ) x a ( b ? ? METHODS TO DETERMINE ORDER OF A REACTION (a) Initial rate method : r = k [A] a [B] b [C] c if [B] = constant [C] = constant then for two different initial concentrations of A we have 1 0 r = k [A 0 ] 1 a , 2 0 r = k [A 0 ] 2 a ? a 2 0 1 0 0 0 ] A [ ] A [ r r 2 1 ? ? ? ? ? ? ? ? ? (b) Using integrated rate law : It is method of trial and error. (c) Method of half lives : for n th order reaction t 1/2 ? 1 n 0 ] R [ 1 ? (d) Ostwald Isolation Method : rate = k [A] a [B] b [C] c = k 0 [A] a METHODS TO MONITOR THE PROGRESS OF THE REACTION : (a) Progress of gaseous reaction can be monitored by measuring total pressure at a fixed volume & temperature or by measuring total volume of mixture under constant pressure and temperature. ? k = t 2.303 log t 0 0 P nP 1) (n P ? ? {Formula is not applicable when n = 1, the value of n can be fractional also.} (b) By titration method : 1. ? a ? V 0 a ? x ? V t ? k = t 2.303 log t 0 V V 2. Study of acid hydrolysis of an easter. k = t 303 . 2 log t 0 V V V V ? ? ? ? (c) By measuring optical rotation produced by the reaction mixture : k = t 303 . 2 log ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? t 0 EFFECT OF TEMPERATURE ON RATE OF REACTION. T.C. = t 10 t K K ? ? 2 to 3 ( for most of the reactions) Arhenius theroy of reaction rate. Products Reactants SH R SH P Ea 1 Ea 2 Threshold enthalpy or energy D S S H = H ? H = Ea ? Ea p R 1 2 Enthalpy (H) Progress of reaction (or reaction coordinate) S S D H = Summation of enthalpies of reactants H = Summation of enthalpies of reactants H = Enthalpy change during the reaction Ea = Energy of activation of the forward reaction Ea = Energy of activation of the backward reaction R P 1 2 E P > E r ? endothermic E P < E r ? exothermic ?H = ( E P ? E r ) = enthalpy change ?H = E af ? E ab E threshold = E af + E r = E b + E p Arhenius equation RT E a Ae k ? ? r = k [conc.] order dT k ln d = 2 a RT E log k = A log T 1 R 303 . 2 Ea ? ? ? ? ? ? ? ? If k 1 and k 2 be the rate constant of a reaction at two different temperature T 1 and T 2 respectively, then we have ? ? ? ? ? ? ? ? ? ? 2 1 a 1 2 T 1 T 1 . R 303 . 2 E k k log ? lnk = ln A ? RT E a slope = ? InA InK E R a 1/T E a ? O ? T ? ? , K ? A. A.Read More
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