We are asked to determine which of the given mechanisms are consistent with the observed rate law:
A. The reaction mechanism that is consistent with the given rate law expression.
When a rate law is given, the reaction mechanism consistent with the rate law is the slow step in the reaction mechanism.
▪ rate law only involves the reactants
▪ the coefficients of the reactants in the slow step are the order of the reaction with respect to that reactant
▪ Rate Law has a general form of:
k = rate constant
X & Y = reactants
a & b = reactant orders
The reaction described by H2(g) + I2(g) yields 2HI(g) has an experimentally determined rate law of rate of reaction= k [H2] [I2] some proposed mechanisms for this reaction are:
1. H2(g) + I2(g) yields (k1 on top of the arrow) 2HI (g) (one step reaction)
(1) I2(g) equilibrium arrow (k1 on top of the arrow, and k-1 on the bottom of the arrow ) 2I (g) (fast equilibrium )
(2) H2(g) + 2I(g) yields (k2 on top of the arrow) 2HI(g) (slow)
(1) I2(g) equilibrium arrow (k1 on top of the arrow, k-1 on the bottom of the arrow) 2I(g)
(2) I(g) +H2(g) equilibrium arrow (k2 on the top and k-2 on the bottom of the equilibrium arrow) yields H2I(g) (Fast equilibrium)
(3) H2I(g) yields ( k3 on top of the arrow) HI(g) + I(g) (slow)
A) which of these mechanisms are consistent with the observed rate law?
a. mechanism a
b. mechanism b
c. mechanism c
B) in 1967 J.H Sullivan showed that this reaction was dramatically catalyzed by light when the energy of the light was sufficient to break the I-I bond in an I2 molecule. Which mechanism(s) are consistent with both the rate law and this additional observation?
a. Mechanism a
b. Mechanism b
c. mechanism c
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