For the reaction A + B → C Time (sec) [A] M [B] M [C] M NO 3 1 0 10 2.2 0.75 0.8 20 1.8 0.65 1.2 30 1.6 0.6 1.3 For this reaction and the formation of B, the rate for the first step is the rate for the second step is M/sec the rate for the third step is M/sec The overall rate of formation of B for this reaction is M/sec 0.025 2 0.01 0.8 0.2 0.013 0.005 0.4 1 M/sec

The reaction H2SeO3(aq) + 6I-(aq) + 4H+(aq) Se(s) + 2I-3(aq) + 3H2O(l) was studied at 0C, and the following data were obtained: [H2SeO3]0 (mol/L) [H+]0 (mol/L) [I]0(mol/L) Initial Rate (mol/L s) 1.0 104 2.0 102 2.0 102 1.66 107 2.0 104 2.0 102 2.0 10-2 3.33 107 3.0 104 2.0 102 2.0 102 4.99 107 1.0 104 4.0 102 2.0 102 6.66 107 1.0 104 1.0 102 2.0 102 0.42 107 1.0 104 2.0 102 4.0 102 13.2 107 1.0 104 1.0 102 4.0 102 3.36 107 These relationships hold only if there is a very small amount of I3 present. What is the rate law and the value of the rate constant? (Assumethatrate=[H2SeO3]t)

The following statements relate to the reaction for the formation of HI: H2(g) + I2(g) -* 2 HI(g) Rate = it[HJ [I2J Determine which of the following statements are true. If a statement is false, indicate why it is incorrect. The reaction must occur in a single step. This is a second-order reaction overall. Raising the temperature will cause the value of k to decrease. Raising the temperature lowers the activation energy' for this reaction. If the concentrations of both reactants are doubled, the rate will double. Adding a catalyst in the reaction will cause the initial rate to increase.

Ammonium cyanate, NH4NCO, rearranges in water to give urea, (NH2)2CO. NH4NCO(aq) (NH2)2CO(aq) Using the data in the table: (a) Decide whether the reaction is first-order or second-order. (b) Calculate k for this reaction. (c) Calculate the half-life of ammonium cyanate under these conditions. (d) Calculate the concentration of NH4NCO after 12.0 hours.

The reaction 2 NO(g) + 2 H2(g) N2(g) + 2 H2O(g) was studied at 904 C, and the data in the table were collected. (a) Determine the order of the reaction for each reactant. (b) Write the rate equation for the reaction. (c) Calculate the rate constant for the reaction. (d) Find the rate of appearance of N2 at the instant when [NO] = 0.350 mol/L and [H] = 0.205 mol/L.

. Account for the increase in reaction rate brought about by a catalyst.

One of the concerns about the use of Freons is that they will migrate to the upper atmosphere, where chlorine atoms can be generated by the following reaction: CCl2F2(g)Freon-12hvCF2Cl(g)+Cl(g) Chlorine atoms can act as a catalyst for the destruction of ozone. The activation energy for the reaction Cl(g) + O3(g) ClO(g) + O2(g) Is 2.1 kJ/mol. Which is the more effective catalyst for the destruction of ozone, Cl or NO? (See Exercise 75.)

Consider the following statements: In general, the rate of a chemical reaction increases a bit at first because it takes a while for the reaction to get warmed up. After that, however, the rate of the reaction decreases because its rate is dependent on the concentrations of the reactants, and these are decreasing. Indicate everything that is correct in these statements, and indicate everything that is incorrect. Correct the incorrect statements and explain.

A reaction is believed to occur by the following mechanism: Stepl: 2AI (Fast equilibrium) Step 2: I + B C (Slow) Overall: 2 A + B C What experimentally determined rate law would lead to this mechanism? (a) Rate = k[A][B] (b) Rate = k[A]2[B] (c) Rate = k[A]2 (d) Rate = k[I][B]

11.51 Peroxyacetyl nitrate (PAN) has the chemical formula CtHjNOj and is an important lung irritant in photochemical smog. An experiment to determine the decomposition kinetics of PAN gave the data below. Determine the order of reaction and calculate the rate constant for the decomposition of PAN. Time, t (min) Partial Pressure of PAN (torr) 0.0 2.00 X 10~’ 10.0 1.61 X 10~} 20.0 1.30 X 10_J 30.0 1.04 X 10"’ 40.0 8.41 X 10-4 50.0 6.77 x 10-4 60.0 5.45 X 10-4