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The rate of a chemical reaction is a measure of how fast the reaction occursThe rate of a chemical reaction is a measure of how fast the reaction occursThe rate of a chemical reaction is a measure of how fast the reaction occursThe rate of a chemical reaction is a measure of how fast the reaction occursThe rate of a chemical reaction is a measure of how fast the reaction occursThe rate of a chemical reaction is a measure of how fast the reaction occurs
DUY TAN UNIVERSITY DEPARTMENT OF NATURAL SCIENCE SUBJECT: CHEMISTRY CHEMISTRY RATE OF A CHEMICAL REACTION 2015 Reaction rate Definition The rate of a chemical reaction is a measure of how fast the reaction occurs 2015 Reaction rate The rate of a chemical reaction is measured as a change in the amounts of reactants or products divided by the change in time Generic reaction: aA + bB → cC + dD ∆ A ∆ B ∆ C ∆ D Rate = − =− = = a ∆t b ∆t c ∆t d ∆t 2015 Reaction rate Exercise The equation for a reaction is: 2NO2(g) + H2O(g) + 1/2O2(g) → 2HNO3 (g) Which one of the following is not numerically equal to the others? ∆ [ NO2 ] A − ∆t ∆ [ H 2O ] C − ∆t ∆ [ O2 ] B − ∆t ∆ [ HNO3 ] D ∆t Answer: B Reaction rate For example Consider the following balanced chemical equation + H2O2 (aq) + 3I (aq) + 2H (aq) → I3 (aq) + 2H2O(l) In the first 10,0 second of the reaction, the concentration of I - from 1.000M to 0,868M Calculate the average of the reaction rate in this time interval 2013 dropped The rate Law: The effect of concentration Consider this reaction: aA + bB → cC + dD m n Rate = k[A] [B] k: rate constant m: the reaction order with respect to A n: the reaction order with respect to B m + n: the overall order The rate law for any reaction must always be determined by experiment 2 The rate Law: The effect of concentration For example: 2NO2(k) + F2(k) → 2NO2F(k) Rate = k[NO2][F2] The rate Law: The effect of concentration EXAMPLE Consider the reaction and the obtained rate / concentration data: A(aq) + B(aq) → C(aq) [A] [B] rate 0.10 0.10 3.10 0.10 0.20 6.10 0.20 0.10 -2 1.2 10 -3 -3 The Effect of Temperature on Reaction Rate The Arhenius equation − Ea k = A.e RT R: the gas constant (8.314 J/mol.K) A: constant called the frequency factor Ea : the activation energy (is an energy barrier or hump that must be surmounted for the reactants to be transformed into products) Thank you