7) Compounds Q and R are known to react in the gas phase to form Compound X by the following overall balanced chemical equation: 2 Q(g) + R(g) → 2X(g) The reaction kinetics have been studied experimentally and the following elementary step sequence was proposed as the reaction mechanism: Step 1: Q+R-Z (slow step, large Ea) • Step 2: Q+Z+2X (fast step, small Ea) Based upon the proposed mechanism, what would be the best way to write the rate law expression for the reaction 2 Q(g) + R(g) → 2X(g)? A. rate = k[Q]²[R] B. rate = k[Q][R] C. rate = = k[R] D. rate = k[Q] [R][Z] E. rate = k[Q][R]²

11.32 The following experimental data were obtained for the reaction 2A + 3 B—C + 2D [A](mol L 1) [B](mol L ’) Rate = A(C]/Af (mol L-1 s-1) 0.127 0.15 0.033 0.127 0.30 0.132 0.255 0.15 0.066 Determine the reaction order for each reactant and the value of the rate constant.

The initial concentration of the reactant in a tirst-order reaction A —» products is 0.64 rnol/L and the half-life is 30.0 s. Calculate the concentration of the reactant exactly 60 s after initiation of the reaction. How long would it take for the concentration of the reactant to drop to one-eighth its initial value? How long would it take for the concentration of the reactant to drop to 0.040 mol/L?

In experiments on the decomposition of azomethane. CH3NHCH3(g)C2H6(g)+N2(g) the following data were obtained: Initial Concentration of Azomethane Initial Rate Exp. 1 1.13 102 M 2.8 106 M/s Exp. 2 2.26 102 M 5.6 106 M/s What is the rate law? What is the value of the rate constant?

The reaction H2(g)+I2(g)2HI(g) may occur by the following mechanism: I2kk12I(fase,equilibrium)I+I+H2k22HI(slow) What rate law is predicted by this mechanism?

Two mechanisms are proposed for the reaction 2NO(g)+O2(g)2NO2(g)Mechanism 1: NO+O2NO3(fast) NO3+NO2NO2(slow) Mechanism 2: NO+ON2O2(fast) N2O2+O22NO2(slow) Show that each of these mechanisms is consistent with the observed rate law: rate=k[ NO2 ]2[ O2 ].

The decomposition of azomethane, (CH3)2N2, to nitrogen and ethane gases is a first-order reaction, (CH3)2N2(g)N2(g)+C2H6(g). At a certain temperature, a 29-mg sample of azomethane is reduced to 12 mg in 1.4 s. (a) What is the rate constant k for the decomposition at that temperature? (b) What is the half-life of the decomposition? (c) How long will it take to decompose 78% of the azomethane?

One possible mechanism for the decomposition of nitryl chloride, NO2CI, is What is the overall reaction? What rate law would be derived from this mechanism? What effect does increasing the concentration of the product NO2 have on the reaction rate?

The thermal decomposition of diacetylene, C4H2, was studied at 950 C. Use the following data (K. C. Hou and H. B. Palmer, Journal of Physical Chemistry. Vol. 60, p. 858, 1965) to determine the order of the reaction.

(Section 11-5) A rule of thumb is that for a typical reaction, if concentrations are unchanged, a 10-K rise in temperature increases the reaction rate by two to four times. Use an average increase of three times to answer the questions below. (a) What is the approximate activation energy of a typical chemical reaction at 298 K? (b) If a catalyst increases a chemical reactions rate by providing a mechanism that has a lower activation energy, then what change do you expect a 10-K increase in temperature to make in the rate of a reaction whose uncatalyzed activation energy of 75 kJ/mol has been lowered to one half this value (at 298 K) by addition of a catalyst?