3. What is the second-order rate constant (k) at 298 K for the simple collision of two radicals? Assume the collision diameter is 5.25 × 10-10 m and the reduced mass is 5.30 × 10-26 kg

The acid-catalyzed iodination of acetone CH3COCH3(aq) + I2(aq) CH3COCH2I(aq) + HI(aq) is a common laboratory experiment used in general chemistry courses to teach the method of initial rates. The reaction is followed spectrophotometrically by the disappearance of the color of iodine in the solution. The following data (J. P. Birk and D. L Walters, Journal of Chemical Education, Vol. 69, p. 585, 1992) were collected at 23 C for this reaction. Determine the rate law for this reaction.

The hydrolysis of the sugar sucrose to the sugars glucose and fructose, C12H22O11+H2OC6H12O6+C6H12O6 follows a first-order rate equation for the disappearance of sucrose: Rate =k[C12H22O11] (The products of the reaction, glucose and fructose, have the same molecular formulas but differ in the arrangement of the atoms in their molecules.) (a) In neutral solution, k=2.11011s1 at 27 C and 8.51011s1 at 37 C. Determine the activation energy, the frequency factor, and the rate constant for this equation at 47 C (assuming the kinetics remain consistent with the Arrhenius equation at this temperature). (b) When a solution of sucrose with an initial concentration of 0.150 M reaches equilibrium, the concentration of sucrose is 1.65107M . How long will it take the solution to reach equilibrium at 27 C in the absence of a catalyst? Because the concentration of sucrose at equilibrium is so low, assume that the reaction is irreversible. (c) Why does assuming that the reaction is irreversible simplify the calculation in pan (b)?

The decomposition of NH3 to N2 and H2 was studied on two surfaces: Surface Ea (kJ/mol) W 163 Os 197 Without a catalyst, the activation energy is 335 kJ/mol. a. Which surface is the better heterogeneous catalyst for the decomposition of NH3? Why? b. How many times faster is the reaction at 298 K on the W surface compared with the reaction with no catalyst present? Assume that the frequency factor A is the same for each reaction. c. The decomposition reaction on the two surfaces obeys a rate law of the form Rate=k[NH3][H2] How can you explain the inverse dependence of the rate on the H2 concentration?

A drug decomposes in the blood by a first-order process. A pill containing 0.500 g of the active ingredient reaches its maximum concentration of 2.5 mg/ 100 mL of blood. If the half-life of the active ingredient is 75 min, what is its concentration in the blood 2.0 h after the maximum concentration has been reached?

The frequency factor A is 6.31 108 L mol1 s1 and the activation energy is 10. kJ/mol for the gas-phase reaction NO(g)+O3(g)NO2(g)+O2(g) which is important in the chemistry of stratospheric ozone depletion. (a) Calculate the rate constant for this reaction at 370. K. (b) Assuming that this is an elementary reaction, calculate the rate of the reaction at 370. K if [NO] = 0.0010 M and [O3] = 0.00050 M.

At 620. K butadiene dimerizes at a moderate rate. The following data were obtained in an experiment involving this reaction: t(s) [C4H6] (mol/L) 0 0.01000 1000.. 0.00629 2000. 0.00459 3000. 0.00361 a. Determine the order of the reaction in butadiene. b. In how many seconds is the dimerization 1.0% complete? c. In how many seconds is the dimerization 10.0% complete? d. What is the half-life for the reaction if the initial concentration of butadiene is 0.0200 M? e. Use the results from this problem and Exercise 45 to calculate the activation energy for the dimerization of butadiene.

Many biochemical reactions are catalyzed by acids. A typical mechanism consistent with the experimental results (in which HA is the acid and X is the reactant) is Step 1: Step 2: Step 3: Derive the rate law from this mechanism. Determine the order of reaction with respect to HA. Determine how doubling the concentration of HA would affect the rate of the reaction.

As with any drug, aspirin (acetylsalicylic acid) must remain in the bloodstream long enough to be effective. Assume that the removal of aspirin from the bloodstream into the urine is a lirst-order reaction, with a half-life of about 3 hours. The instructions on an aspirin bottle say to take 1 or 2 tablets every 4 hours. If a person takes 2 aspirin tablets, how much aspirin remains in the bloodstream when it is time for the second dose? (A standard tablet contains 325 mg of aspirin.)

Explain how a species might be part of a rate law but not part of a balanced chemical reaction.