The rate at which a certain drug is eliminated by the body follows first-order kinetics, with a half life of 77 minutes. Suppose in a particular patient the concentration of this drug in the bloodstream immediately after injection is 0.79 µg/mL. What will the concentration be 154 minutes later? Round your answer to 2 significant digits. OP Hydrogen-3 is radioactive and has a half life of 12.3 years. How much of a 8.70 mg sample would be left after 22.9 years? Round your answer to 2 significant digits. Also, be sure your answer has a unit symbol. 0 X H

The rate at which a certain drug is eliminated by the body follows first-order kinetics, with a half life of 77 minutes. Suppose in a particular patient the concentration of this drug in the bloodstream immediately after injection is 0.79 µg/mL. What will the concentration be 154 minutes later? Round your answer to 2 significant digits. OP Hydrogen-3 is radioactive and has a half life of 12.3 years. How much of a 8.70 mg sample would be left after 22.9 years? Round your answer to 2 significant digits. Also, be sure your answer has a unit symbol. 0 X H

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter12: Chemical Kinetics

Section: Chapter Questions

Problem 44E: At 500 K in the presence of a copper surface, ethanol decomposes according to the equation...

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When enzymes are present at very low concentration, their effect on reaction rate can be described by first-order kinetics. Calculate by what factor the rate of an enzyme-catalyzed reaction changes when the enzyme concentration is changed from 1.5 107 M to 4.5 106 M.
One experimental procedure that can be used to determine the rate law of a reaction is the method of initial rates. What data are gathered in the method of initial rates, and how are these data manipulated to determine k and the orders of the species in the rate law? Are the units for k. the rate constant, the same for all rate laws? Explain. If a reaction is first order in A, what happens to the rate if [A] is tripled? If the initial rate for a reaction increases by a factor of 16 when [A] is quadrupled, what is the order of n? If a reaction is third order in A and [A] is doubled, what happens to the initial rate? If a reaction is zero order, what effect does [A] have on the initial rate of a reaction?
The hydrolysis of the sugar sucrose to the sugars glucose and fructose follows a first-order rate equation for the disappearance of sucrose. C12H22O11(aq)+H2O(l)C6H12O6(aq)+C6H12O6(aq) Rate =k[C12H22O11] In neutral solution, k=2.11011 at 27 C. (As indicated by the rate constant, this is a very slow reaction. In the human body, the rate of this reaction is sped up by a type of catalyst called an enzyme.) (Note: That is not a mistake in the equation—the products of the reaction, glucose and fructose, have the same molecular formulas, C6H12O6, but differ in the arrangement of the atoms in their molecules). The equilibrium constant for the reaction is 1.36105 at 27 C. What are the concentrations of glucose, fructose, and sucrose after a 0.150 M aqueous solution of sucrose has reached equilibrium? Remember that the activity of a solvent (the effective concentration) is 1.
11.41 For a drug to be effective in treating an illness, its levels in the bloodstream must be maintained for a period of time. One way to measure the level of a drug in the body is to measure its rate of appearance in the urine. The rate of excretion of penicillin is first order, with a half-life of about 30 min. If a person receives an injection of 25 mg of penicillin at t = 0, how much penicillin remains in the body after 3 hours?
The reaction of NO2(g) and CO(g) is thought to occur in two steps to give NO and CO2: Step 1: Slow NO2(g) + NO2(g) NO(g) + NO3(g) Step 2: Fast NO3(g) + CO(g) NO2(g) + CO2(g) (a) Show that the elementary steps add up to give the overall, stoichiometric equation. (b) What is the molecularity of each step? (c) For this mechanism to be consistent with kinetic data, what must be the experimental rate equation? (d) Identify any intermediates in tins 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.)
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)?
An excellent way to make highly pure nickel metal for use in specialized steel alloys is to decompose Ni(CO)4 by heating it in a vacuum to slightly above room temperature. Ni(CO)4(g) Ni(s) + 4 CO(g) The reaction is proposed to occur in four steps, the first of which is Ni(CO)4(g) Ni(CO)3(g) + CO(g) Kinetic studies of this first-order decomposition reaction have been carried out between 47.3 C and 66.0 C to give the results in the table. (a) Determine the activation energy for this reaction. (b) Ni(CO)4 is formed by the reaction of nickel metal with carbon monoxide. Suppose that 2.05 g CO is combined with 0.125 g nickel metal. Determine the maximum mass (g) of Ni(CO)4 that can be formed. Replacement of CO by another molecule in Ni(CO)4 was studied in the nonaqueous solvents toluene and hexane to understand the general principles that govern the chemistry of such compounds. Ni(CO)4(g) + P(CH3)3 Ni(CO)3P(CH3)3 + CO A detailed study of the kinetics of the reaction led to the mechanism Step1:(slow)Ni(CO)4Ni(CO)3+COStep2:(fast)Ni(CO)3+P(CH3)3Ni(CO)3P(CH3)3 (c) Which step in the mechanism is unimolecular? Which is bimolecular? (d) Add the steps of the mechanism to show that the result is the balanced equation for the observed reaction. (e) Is there an intermediate in this reaction? If so, what is it? (f) It was found that doubling the concentration of Ni(CO)4 increased the reaction rate by a factor of 2. Doubling the concentration of P(CH3)3 had no effect on the reaction rate. Based on this information, write the rate equation for the reaction. (g) Does the experimental rate equation support the proposed mechanism? Why or why not?
For the reaction of phenyl acetate with water the concentration as a function of time was given in Question 11. Assume that the concentration of water does not change during the reaction. Analyze the data from Question 11 to determine (a) the rate law. (b) the order of the reaction with respect to phenyl acetate. (c) the rate constant. (d) the rate of reaction when the concentration of phenyl acetate is 0.10 mol/L (assuming that the concentration of water is the same as in the experiments in the table in Question 11).
At 500 K in the presence of a copper surface, ethanol decomposes according to the equation C2H5OH(g)CH3CHO(g)+H2(g) The pressure of C2H5OH was measured as a function of time and the following data were obtained: Time(s) PC2H5OH(torr) 0 250. 100. 237 200. 224 300. 211 400. 198 500. 185 Since the pressure of a gas is directly proportional to the concentration of gas, we can express the rate law for a gaseous reaction in terms of partial pressures. Using the above data, deduce the rate law, the integrated rate law, and the value of the rate constant, all in terms of pressure units in atm and time in seconds. Predict the pressure of C2H5OH after 900. s from the start of the reaction. (Hint: To determine the order of the reaction with respect to C2H5OH, compare how the pressure of C2H5OH decreases with each time listing.)