2- The gas-phase reaction 2N02 + O3 N 205 + 02 has the rate constant k = 2.0 × 1

Question

2- The gas-phase reaction 2N02 + O3 N 205 + 02 has the rate constant k = 2.0 × 104 L/mols at 300 K. What is the order of this reaction? (25 points) -E andB- ky 3- Write down d[Bldt for B F. (25 points) 4- The second-order rate constants for the reaction of oxygen atoms with with benzene the te constants are 1.44 x 107 L/mhols at 300.3 K, 3.03 07 Lmols at 341.2 K. Find the pre-exponential factor and activation energy of the reaction. (25 points) 5- A reaction is first order respect to the substance A and 2nd order respect to B. Write down the corresponding rate law. For a constant initial concentration of [A], the initial rate is measured for different initial concentrations of B. Using these experimental data, explain how we can obtain the rate constant. (25 points) a. b.

Explanation / Answer

Ans 1: General equation to relate order and rate constant

For a reaction of (x + y + z + ...) order rate constant can be written as mol1-(x+y+z+---).L(x+y+z+---)-1.s-1 For this reaction (x+y+z+---) should be equal to 2 so the rate units matches. Order will be "2".

Ans 2: K1B = K-1E ---equa 1 where Keq = forward/backward = K1/K-1

and d[B]/dt = formation of B = K-1[E] - K1[B] ---equa 2

from equa 1 and 2 B = (K-1/K1)E = E/Keq

d[B]/dt = [E](K-1 - K1/Keq)

Similarly for other part

Ans 3: From relative arhenius equation

ln(k2/k1) = Ea/R (1/T1 - 1/T2)

ln(3.03/1.44) = Ea/8.314 (1/300.3 -1/341.2)

Ea = 0.7439R/(3.9917X10-4)

Ea = 15494 J/mol

Ans 4: a) Reaction A + B -> C + D

rate = k[A][B] But if concentration of B is very high

rate = k'[A] wher k' = k[B] hence reaction will be of first order with respect to A and second order with respect to B.

b) Suppose if B is in excess then we can perform an experiment to calculate the product concentration (say C) then k' can be calculate like for first order reaction by plotting a graph between [ln (C-A)] vs time

and k' can be calculated and actual value of k can be calculate by least square method or equation k = k'(B-m) wherr m is mean of C over varied ranges.

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