Q&A Hero

Q: The reaction: 2 HI -> H2 + I2, is second order and the rate constant at 800 K is 9.70 10-2 M-1 s-1. How long will it take for 8.00 10-2 mol/L of HI to decrease to one-fourth of its initial concentration?A) 0.619 sB) 124 sC) 387 sD) 429 s

Q: The second-order reaction, 2 Mn(CO)5 -> Mn2(CO)10 has a rate constant equal to 3.0 109 M-1s-1 at 25C. If the initial concentration of Mn(CO)5 is 1.0 10-5 M, how long will it take for 90.% of the reactant to disappear?A) 3.3 10-16 sB) 3.7 10-15 sC) 3.0 10-4 sD) 3.0 103 s

Q: In aqueous solution, hypobromite ion, BrO-, reacts to produce bromate ion, BrO3-, and bromide ion, Br-, according to the following chemical equation.3 BrO-(aq) -> BrO3-(aq) + 2 Br-(aq)A plot of 1/[BrO-] vs. time is linear and the slope is equal to 0.056 M-1s-1. If the initial concentration of BrO- is 0.80 M, how long will it take one-half of the BrO- ion to react?A) 4.5 10-2 sB) 7.1 sC) 12 sD) 22 s

Q: A plot of 1/[BrO-] vs time is linear for the reaction:3 BrO-(aq) -> BrO3-(aq) + 2 Br-(aq)What is the order of the reaction with respect to the hypobromite ion, BrO-?A) 0B) 1C) 2D) 3

Q: A researcher needs 5.00 mg of 128Ba for an experiment. If the half-life of 128Ba is 2.43 days, how many milligrams of 128BaCl2 must she order from the manufacturer if it takes 4.50 days to ship the material from the manufacturer to the university? (Assume the molar mass of 128Ba is 128 g/mol.) A) 11.6 mg B) 18.0 mg C) 21.5 mg D) 44.9 mg

Q: An experiment with 55Co takes 47.5 hours. At the end of the experiment, 1.90 ng of 55Co remains. If the half life is 18.0 hours, how many ng of 55Co were originally present? A) 2.47 ng B) 3.05 ng C) 3.28 ng D) 11.8 ng

Q: What is the decay constant for a radioactive isotope which decreases to 34% of its original value in 2.48 hours? A) 0.137 hr-1 B) 0.168 hr-1 C) 0.435 hr-1 D) 2.30 hr-1

Q: Fluorine-18 is an isotope used in Positron Emission Tomography (PET) to scan the brain. If a researcher has 1.50 g of 18F, how long before it decays to 1.0 ng? The half-life of 18F is 109.8 minutes.A) 5.2 10-2 hrB) 4.6 10-2 hrC) 19 hrD) 51 hr

Q: Fluorine-18 is a radioisotope widely used in positron emission tomography to investigate brain activity. The half-life is 109.8 minutes. How long will it take for 2.75 g of 18F to decay to 500 ng?A) 0.288 minB) 270 minC) 871 minD) 2.06 103 min

Q: What percentage of a radioactive substance remains after 6.00 half-lives have elapsed? A) 0.78% B) 1.56% C) 3.31% D) 6.25%

Q: If a sample of 233Pa takes 62.7 days to decrease to 20.0% of its original mass, what is its half-life? A) 0.0370 days B) 27.0 days C) 157 days D) 195 days

Q: Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239Np to decay to 1.00% of its original quantity? A) 0.0640 days B) 0.736 days C) 1.36 days D) 15.6 days

Q: Iodine-123, used in thyroid therapy, has a half-life of 13.27 hours. How many half-lives are required for a 160 mg sample of iodine-123 to decay to 5.0 mg? A) 0.031 B) 1.0 C) 5.0 D) 32

Q: The decay constant, k, is given for each of the beta emitters below. Which one has the shortest half life? A) 36Cl, 7.09 10-24 s-1 B) 131I, 9.94 10-7 s-1 C) 42K, 1.55 10-5 s-1 D) 63Ni, 2.39 10-10 s-1

Q: For the first-order reaction, 2 N2O(g) -> 2 N2(g) + O2(g), what is the concentration of N2O after 3 half-lives if 0.15 mol of N2O is initially placed into in a 1.00-L reaction vessel?A) 9.4 10-3 MB) 1.9 10-2 MC) 3.8 10-2 MD) 7.5 10-2 M

Q: The first-order reaction, SO2Cl2 -> SO2 + Cl2, has a half-life of 8.75 hours at 593 K. How long will it take for the concentration of SO2Cl2 to fall to 12.5% of its initial value?A) 0.165 hrB) 3.22 hrC) 6.06 hrD) 26.2 hr

Q: Acetaldehyde decomposes at 750 K: CH3CHO -> CO + CH4. The reaction is first order in acetaldehyde and the half-life of the reaction is found to be 530 seconds. What is the rate constant for the reaction at this temperature?A) 2.7 x 10-3 s-1B) 1.3 x 10-3 s-1C) 2.7 x 102 s-1D) 7.6 x 102 s-1

Q: The half life of the reaction shown below is found not to depend on the concentration of H2O2(aq).2 H2O2(aq) -> 2 H2O(l) + O2(g)What is the order of this reaction?A) zerothB) firstC) secondD) third

Q: The decomposition of cyclopropane, was observed at 500C and its concentration was monitored as a function of time. The data set is given below. What is the order of the reaction with respect to cyclopropane? A) zero B) first C) second D) third

Q: The following reaction is first order: C2H6 -> 2 CH3. If the rate constant is equal to 5.5 10-4 s-1 at 1000 K, how long will it take for 0.35 mol of C2H6 in a 1.00 L container to decrease to 0.10 mol in the same container?A) 7.6 minB) 38 minC) 106 minD) 131 min

Q: The isomerization reaction, CH3NC -> CH3CN, is first order and the rate constant is equal to0.46 s-1 at 600 K. What is the concentration of CH3NC after 0.20 minutes if the initial concentration is 0.10 M?A) 4.0 x 10-4 MB) 9.1 x 10-4 MC) 4.0 x 10-2 MD) 9.1 x 10-2 M

Q: The first-order reaction, 2 N2O(g) -> 2 N2(g) + O2(g), has a rate constant equal to 0.76 s-1 at1000 K. How long will it take for the concentration of N2O to decrease to 42% of its initial concentration?A) 0.88 sB) 1.1 sC) 1.8 sD) 2.4 s

Q: The first-order reaction, SO2Cl2 -> SO2 + Cl2, has a rate constant equal to 2.20 10-5 s-1 at593 K. What percentage of the initial amount of SO2Cl2 will remain after 2.00 hours?A) 1.00%B) 14.7%C) 17.1%D) 85.4%

Q: For a particular first-order reaction, it takes 48 minutes for the concentration of the reactant to decrease to 25% of its initial value. What is the value for rate constant (in s-1) for the reaction? A) 1.0 10-4 s-1 B) 4.8 10-4 s-1 C) 6.0 10-3 s-1 D) 2.9 10-2 s-1

Q: The first-order decomposition of hydrogen peroxide occurs according to the equation2 H2O2(aq) -> 2 H2O(l) + O2(g)Using data from a concentration-time study of this reaction, which plot will produce a straight line?A) [H2O2] versus timeB) [H2O2]2 versus timeC) 1/[H2O2] versus timeD) ln[H2O2] versus time

Q: The following set of data was obtained by the method of initial rates for the reaction:S2O82-(aq) + 3 I-(aq) -> 2 SO42-(aq) + I3-(aq)What is the initial rate when S2O82- is 0.15 M and I- is 0.15 M?A) 4.10 10-6 M s-1B) 8.10 10-3 M s-1C) 1.22 10-2 M s-1D) 5.40 10-2 M s-1

Q: The following set of data was obtained by the method of initial rates for the reaction:S2O82-(aq) + 3 I-(aq) -> 2 SO42-(aq) + I3-(aq)What is the rate law for the reaction?A) Rate = k[S2O82-][I-]B) Rate = k[S2O82-][I-]5C) Rate = k[S2O82-][I-]2D) Rate = k[S2O82-]2[I-]

Q: The following set of data was obtained by the method of initial rates for the reaction:BrO3-(aq) + 5 Br-(aq) + 6 H+(aq) -> 3 Br2(aq) + 3 H2O(l).Calculate the initial rate when BrO3- is 0.30 M, Br- is 0.050 M, and H+ is 0.15 M.A) 6.1 10-5 M/sB) 2.7 10-3 M/sC) 5.3 10-2 M/sD) 8.4 10-2 M/s

Q: The following set of data was obtained by the method of initial rates for the reaction:BrO3-(aq) + 5 Br-(aq) + 6 H+(aq) -> 3 Br2(aq) + 3 H2O(l).What is the rate law for the reaction?A) Rate = k[BrO3-][Br-][H+]4B) Rate = k[BrO3-][Br-][H+]-4C) Rate = k[BrO3-][Br-][H+]-2D) Rate = k[BrO3-][Br-][H+]2

Q: The following set of data was obtained by the method of initial rates for the reaction:(H3C)3CBr + OH- -> (H3C)3COH + Br-What is the value of the rate constant, k?A) 8.8 10-4 s-1B) 4.4 10-4 s-1C) 1.8 10-4 s-1D) none of these

Q: The following set of data was obtained by the method of initial rates for the reaction:(H3C)3CBr + OH- -> (H3C)3COH + Br-What is the order of reaction with respect to ion, OH-?A) zeroB) firstC) secondD) none of these

Q: The following set of data was obtained by the method of initial rates for the reaction:2 HgCl2(aq) + C2O42-(aq) -> 2 Cl-(aq) + 2 CO2(g) + Hg2Cl2(s)What is the value of the rate constant, k?A) 1.4 10-8 1/M2 sB) 1.3 10-7 1/M2 sC) 1.4 10-5 1/M2 sD) 1.3 10-4 1/M2 s

Q: The following set of data was obtained by the method of initial rates for the reaction:2 HgCl2(aq) + C2O42-(aq) -> 2 Cl-(aq) + 2 CO2(g) + Hg2Cl2(s)What is the rate law for the reaction?A) Rate = k[HgCl2][C2O42-]-2B) Rate = k[HgCl2][C2O42-]-1C) Rate = k[HgCl2]2[C2O42-]D) Rate = k[HgCl2][C2O42-]2

Q: Using the method of initial rates for the reaction A -> B, if the initial concentration of A is doubled and the rate of reaction quadruples, what is the order of reaction with respect to A?A) zerothB) firstC) secondD) fourth

Q: If the units for rate are M s-1, what are the units for the rate constant, k, if the overall order of the reaction is three? A) s-1 B) M2 s-1 C) M-1 s-1 D) M-2 s-1

Q: Chlorine reacts with chloroform according to the reaction given below:Cl2 + CHCl3 -> CCl4 + HClWhen the initial concentration of Cl2 is doubled the reaction rate increases by a factor of 1.41. What is the order of the reaction with respect to Cl2?A) -1/2B) -1C) 1/2D) 2

Q: Iodide and hypochlorite ion react in aqueous solution according to the reaction below:I- + OCl- -> OI- + Cl-If the concentration of OH- in the solution is doubled, the rate of the reaction is halved. What is the order of the reaction with respect to OH-?A) -2B) -1C) +1D) +2

Q: What is the overall reaction order for the reaction that has the rate law: Rate = k[H2][NO]2? A) zero order B) first order C) second order D) third order

Q: Cerium(IV) ion reacts with thallium(I) ion in a one-step reaction shown below:2 Ce4+(aq) + Tl+(aq) -> 2 Ce3+(aq) + Tl3+(aq).If the rate law is: Rate = k[Ce4+]2[Tl+], what is the overall order of the reaction?A) firstB) secondC) thirdD) fourth

Q: The decomposition of ammonia to nitrogen and hydrogen on a tungsten filament at 800C is independent of the concentration of ammonia at high pressures of ammonia. What is the order of the reaction with respect to ammonia? A) zero B) first C) second D) third

Q: Given the following hypothetical reaction: 2 E(g) + F(g) + G(g) -> products.If the rate law is: Rate = k[E]2[F]-1, what is the overall order of reaction?A) zeroB) firstC) secondD) third

Q: Given the following hypothetical reaction: 2 E(g) + F(g) + G(g) -> products.If the rate law is: Rate = k[E]2[F]-1, what is the order of reaction with respect to E?A) zeroB) firstC) secondD) third

Q: The hydrolysis of tert-butyl chloride is given in the reaction below:(CH3)3CCl(aq) + H2O(l) -> (CH3)3COH(aq) + H+(aq) + Cl-(aq)If the rate law is: Rate = k[(CH3)3CCl], what is the order of the reaction with respect to water?A) zeroB) firstC) secondD) third

Q: The reaction between chlorine and nitric oxide to form nitrosyl chloride is shown below. If the reaction rate doubles when the concentration of Cl2 is doubled and the rate quadruples when the concentration of NO is doubled, by what factor will the rate increase if both concentrations, NO and Cl2, are doubled?Cl2(g) + 2 NO(g) -> 2 NOCl(g)A) 2B) 4C) 8D) 16

Q: For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of reaction if the concentration of B is increased by a factor of 2.00? The rate will A) decrease by a factor of 1/4.00. B) decrease by a factor of 1/2.00. C) increase by a factor of 2.00. D) increase by a factor of 4.00.

Q: For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of reaction if the concentration of A is increased by a factor of 3.00? The rate will A) decrease by a factor of 1/9.00. B) decrease by a factor of 1/3.00. C) increase by a factor of 3.00. D) increase by a factor of 9.00.

Q: The reaction shown below has the rate law: Rate = k[BrO3-][Br-][H+]2.BrO3-(aq) + 5 Br-(aq) + 6 H+(aq) -> 3 Br2(aq) + 3 H2O(l)What is the overall order of reaction?A) firstB) secondC) thirdD) fourth

Q: The reaction below is first order in H2 and second order in NO. What is the rate law for this reaction?2 H2(g) + 2 NO(g) -> N2(g) + 2 H2O(g)A) Rate = 2k[H2][NO]B) Rate = k[H2][NO]2C) Rate = k[H2]2[NO]2D) Rate = 2k[H2]2[NO]2

Q: For the reaction shown below, what is the order of reaction with respect to Br-?ClO2-(aq) + 4 Br-(aq) + 4 H+(aq) -> Cl-(aq) + 2 Br2(aq) +2 H2O(l)A) 1st orderB) 2nd orderC) 4th orderD) can"t tell from the information provided

Q: Which statement is true for the general rate law: Rate = k[A]m[B]n? A) It can be written from the stoichiometry of the overall reaction. B) The overall order of the reaction is equal to m times n. C) The values for the exponents must be determined by experiment. D) The exponents in the rate law must be positive integers.

Q: A concentration-time study of the gas phase reaction 2 A3 -> 3 A2 produced the data in the table below.Time (s) [A3] (M) [A2] (M)0 4.00 10-4 010 2.00 10-4 3.00 10-420 1.00 10-4 4.50 10-430 5.00 10-5 ?What is the concentration of A2 after 30 seconds?A) 5.00 10-4 MB) 5.25 10-4 MC) 5.50 10-4 MD) 6.00 10-4 M

Q: A concentration-time study of the gas phase reaction 2 A3 -> 3 A2 produced the data in the table below.Time (s) [A3] (M) [A2] (M)0 4.00 10-4 010 2.00 10-4 3.00 10-420 1.00 10-4 4.50 10-430 5.00 10-5 ?What is the average rate of formation of A2 in the time interval 20-30 seconds?A) 6.00 10-4 M/sB) 5.25 10-5 M/sC) 7.50 10-6 M/sD) 6.00 10-6 M/s

Q: A concentration-time study of the gas phase reaction 2 A3 -> 3 A2 produced the data in the table below.Time (s) [A3] (M) [A2] (M)0 4.00 10-4 010 2.00 10-4 3.00 10-420 1.00 10-4 4.50 10-430 5.00 10-5 ?What is the average rate of decomposition of A3 in the time interval 20-30 seconds?A) 4.00 10-4 M/sB) 3.50 10-5 M/sC) 5.00 10-6 M/sD) 4.00 10-6 M/s

Q: Hydrogen peroxide decomposes to water and oxygen according to the reaction below:2 H2O2(aq) -> 2 H2O(l) + O2(g)In the presence of large excesses of I- ion, the following set of data is obtained. What is the average rate of disappearance of H2O2(aq) in M/s in the first 45.0 seconds of the reaction if 1.00 L of H2O2 reacts at 25C and 1.00 atm pressure?A) 9.09 10-7 M/sB) 3.63 10-6 M/sC) 4.33 10-5 M/sD) 1.64 10-4 M/s

Q: The decomposition of dinitrogen pentoxide is described by the chemical equation2 N2O5(g) -> 4 NO2(g) + O2(g)If the rate of appearance of O2 is equal to 2.40 mol/min at a particular moment, what is the rate of disappearance of N2O5 at that moment?A) 0.600 mol/minB) 1.20 mol/minC) 4.80 mol/minD) 9.60 mol/min

Q: The decomposition of dinitrogen pentoxide is described by the chemical equation2 N2O5(g) -> 4 NO2(g) + O2(g)If the rate of disappearance of N2O5 is equal to 1.40 mol/min at a particular moment, what is the rate of appearance of NO2 at that moment?A) 0.700 mol/minB) 1.40 mol/minC) 2.80 mol/minD) 5.60 mol/min

Q: The reaction that occurs in a Breathalyzer, a device used to determine the alcohol level in a person's bloodstream, is given below. If the rate of appearance of Cr2(SO4)3 is 1.24 mol/min at a particular moment, what is the rate of disappearance of C2H6O at that moment? A) 0.413 mol/min B) 0.826 mol/min C) 1.86 mol/min D) 3.72 mol/min

Q: For the reaction shown below, what is the relationship between the rate of formation of Br2 and the rate of reaction of Br- over the same time period?ClO2-(aq) + 4 Br-(aq) + 4 H+(aq) -> Cl-(aq) + 2 Br2(aq) +2 H2O(l)A) rate of formation of Br2 = 1/2 rate of reaction of Br-B) rate of formation of Br2 = 1/4 rate of reaction of Br-C) rate of formation of Br2 = 2 rate of reaction of Br-D) rate of formation of Br2 = 2 rate of reaction of Br-

Q: Hydroquinone, HOC6H6OH, can be formed by the reaction with acetylene below:2 HCCH + 3 CO + H2O -> HOC6H4OH + CO2How is the rate of disappearance of acetylene, HCCH, related to the appearance of hydroquinone (Hq)?= ?A) B) C) D)

Q: Methanol can be produced by the following reaction:CO(g) + 2 H2(g) -> CH3OH(g).How is the rate of disappearance of hydrogen gas related to the rate of appearance of methanol?= ?A) B) C) D) none of these

Q: Molecular hydrogen can be made from methane gas by the reaction below. How is the rate of disappearance of CH4 related to the rate of appearance of H2?= ?CH4 (g) + H2O (l) -> CO (g) + 3H2 (g)A) B) C) D) none of these

Q: "Instantaneous rate" is defined as the A) change in concentration per unit time. B) equation showing how the rate depends on the concentration of each reactant. C) rate of reaction at a particular time. D) rate of reaction during a time interval.

Q: Which term describes the measure of the increase in the concentration of a product per unit time? A) activation energy B) kinetics C) reaction rate D) reaction time

Q: Platinum in the catalytic converter of an automobile catalyzes the conversion of CO to CO2 is an example of a ________ (heterogeneous, homogeneous) catalyst.

Q: Hydrochloric acid in the hydrolysis of an ester to form an alcohol and a carboxylic acid is an example of a ________ (heterogeneous, homogeneous) catalyst.

Q: An aqueous reaction occurs by a two-step mechanism, shown below.Step 1: A2X2 + Y -> A2X + XYStep 2: A2X2 + XY -> A2X + X2 + YIn this reaction the intermediate is ________, and the catalyst is ________.

Q: A reaction with an activation energy, Ea = 103 kJ/mol has a rate constant, k = 3.5 10-5 s-1 at 25C. For this reaction the rate constant at 45C is ________.

Q: A reaction with an activation energy, Ea = 51.2 kJ/mol will proceed ________ times faster when the temperature is raised from 20 C to 30 C.

Q: A reaction has a rate constant, k = 1.2 10-12 s-1 at 273 K and k = 5.1 10-7 s-1 at 373 K has an activation energy, Ea = ________ kJ/mol.

Q: A gaseous reaction occurs by a two-step mechanism, shown below.Step 1: AX +Y2 -> AXY2Step 2: AXY2 + AX -> 2 AXYIf the rate law for this reaction is Rate = k[AX]2[Y2], the intermediate is ________, and step ________ is the rate-determining step.

Q: A reaction occurs by a two-step mechanism, shown below.Step 1: AX2(g) -> AX(g) + X(g)Step 2: AX2(g) + X(g) -> AX + X2(g)The intermediate in this reaction is ________, and the molecularity of the second step is ________.

Q: The rate-determining step in a reaction is shown below. The molecularity of this reaction is ________.NO2(g) + NO2(g) -> NO(g) + NO3(g)

Q: A gaseous compound, C, undergoes catalytic decomposition at an initial rate of 0.45 M/s when[C]o = 3.0 10-3 M and 0.45 M/s when [C]o = 9.0 10-3 M. Therefore, this is a ________ order reaction.

Q: At an elevated temperature the decomposition of a gaseous oxide, AO2 occurs with a rate constant,k = 0.54 M-1s-1. If the half-life of this reaction is 926 seconds when [AO2] = 2.0 10-3 M and 462 seconds when [AO2] = 4.0 10-3 M, this reaction is ________ order.

Q: has a decay constant, k = 1.209 10-4 yr-1 and a half-life of ________ years.

Q: At 55 the decomposition of N2O5 is first order, having a rate constant, k = 1.7 10-3 s-1. If the initial concentration of N2O5 is 6.4 10-3 M, the number of half-lives that are required for the N2O5 concentration to fall to 2.0 10"4 M is ________, and the amount of time required is ________ minutes.

Q: The decomposition of hydrogen peroxide occurs according to the equation2 H2O2(aq) -> 2 H2O(l) + O2(g)A concentration-time study of this reaction produces a straight line when ln[H2O2] is plotted versus time. Therefore, this is a ________ order reaction.

Q: At 300C decomposition of NO2(g) occurs with a rate law: Rate = - k[NO2]x. If the initial rate of decomposition is 3.2 10-5 M/s when [NO2]o = 8.0 10"3 M and the initial rate of decomposition is 8.0 10-6 M/s when [NO2]o = 4.0 10-3 M, then the order of reaction with respect to NO2, x = ________.

Q: A reaction is second order in NO and first order in O2 has a rate constant, k = 1.4 104 M-2s-1. What is the initial rate of reaction when the concentrations of NO and O2 are 0.015 M and 0.030 M, respectively?

Q: The reaction below is second order in ClO2 and first order in OH-. When the concentration of ClO2 is 0.020 M and the concentration of OH- is 0.10 M, the initial rate of reaction is 8.00 10-4 M/s. What is the rate constant, k, for this reaction?2 ClO2(aq) + 2 OH-(aq) -> ClO3-(aq) + ClO2-(aq) + H2O(l)