Which statement about the slow step in the mechanism for a reaction is true? It
ID: 980156 • Letter: W
Question
Which statement about the slow step in the mechanism for a reaction is true? It has a rate that is independent of the activation energy for the reaction. It limits the effectiveness of the catalyst. It controls the rate at which the products are produced. It almost always involves the breaking of hydrogen bonds. It determines the value of the standard enthalpy of the reaction for the reaction. The reaction: A + 3B rightarow D + F was studied carefully and the following mechanism was finally determined. A + B doubleheadarrow C (fast) C + B doubleheadarrow D + E (slow) E + B doubleheadarrow F (very fast) The rate law for the reaction would therefore be rate=k[A]^2[B] rate=k[A][B]^2 rate=k[C][B] rate=k[A][B]^3 rate=k[A]^2[B] The reaction of substance A with substance C was carefully studied under conditions where the [C] remained essentially constant The graph of [A] versus time gave a straight line while the graph of ln[A] vs. time and that of 1/[A] vs. time both gave curves. The reaction is therefore zero order with respect to A The reaction is therefore one-half order with respect to A The reaction is therefore first order with respect to A The reaction is therefore second order with respect to A The reaction is therefore third order with respect to A For a particular chemical reaction, the rate constant at 30.0 degree C is 1.38 Times 10^-4 L/molsec, while the value at 49.0 degree C is 1.21 Times 10^-3 L/molsec. What is the activation energy for this reaction? 92.8 kJ 200. kJ 40.4 kJ 343 kJ 56.4kJExplanation / Answer
Answer: According to the given data
20] Here the correct statement is option [C] it controls the rate at which the products are produced.
21] The rate is depend upon the slow step and hence the correct option is [C] rate = K [C] [B]
22] Here as per the given informations the correct option is [C] the reaction is first order with respect to [A] .
23] Here we have to use the formula
Ln K1/K2 = - Ea/R [ 1/T1 - 1/T2] [ Temperatures must be in Kelvin , R = 8.314 ]
Now putting all the given values we get
log 1.38 * 10-4 / 1.21 * 10-3 = - Ea/ 2.303 * 8.314 [ 1/303 - 1/ 322]
log[ 11.4049 ] = - Ea / 19.147 [ 0.0033 - 0.0031]
1.057 = -Ea/ 19.147 [ 0.0002]
Ea = - 1.057 / 1.0445 * 10-5
is nearlly equal to 102 Kj and for 1 it is equal to 56.4KJ
and hence the required answer is 56.4 KJ
THANK YOU :)
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.