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Chemistry
Q:
Shown is a concentration versus time plot for a reaction involving gases A, B, and C.Which equation best represents the reaction?A) 4A(g) -> B(g) + 2C(g)B) 4A(g) + B(g) -> 2C(g)C) 2C(g) -> 4A(g) + B(g)D) 2C(g) + B(g) -> 4A(g)
Q:
The Haber process is the synthesis of ammonia gas from hydrogen and nitrogen on a hot metal surface. What is the catalyst and what type of catalysis is occurring?A) H2, homogeneousB) N2, homogeneousC) NH3, homogeneousD) metal surface, heterogeneous
Q:
A mechanism for a naturally occurring reaction that destroys ozone is:Step 1: O3(g) + HO(g) -> HO2(g) + O2(g)Step 2: HO2(g) + O(g) -> HO(g) + O2(g)Which species is a catalyst and what type of catalysis is occurring?A) HO, homogeneousB) HO, heterogeneousC) HO2, homogeneousD) HO2, heterogeneous
Q:
An aqueous reaction occurs by a two-step mechanism, shown below.Step 1: A2X2 + Y -> A2X + XYStep 2: A2X2 + XY -> A2X + X2 + YWhat is the catalyst in this reaction?A) A2XB) X2C) XYD) Y
Q:
Which of the following does not affect the rate of a bimolecular reaction?
A) concentrations of reactants
B) presence of a catalyst
C) temperature
D) All of the above affect the rate.
Q:
The decomposition of ozone in the stratosphere can occur by the following two-step mechanism:Br + O3 -> BrO + O2BrO + O -> Br + O2Which species is a catalyst in this mechanism?A) BrB) BrOC) OD) O3
Q:
A mechanism for a naturally occurring reaction that destroys ozone is:Step 1: O3(g) + HO(g) -> HO2(g) + O2(g)Step 2: HO2(g) + O(g) -> HO(g) + O2(g)Which species is a catalyst?A) HOB) HO2C) OD) O3
Q:
The decomposition of hydrogen peroxide is given by the following reaction:2 H2O2(aq) -> 2 H2O(l) + O2(g)In the presence of KI the reaction is thought to occur by the following mechanism:Step 1: H2O2 + I- -> H2O + IO-Step 2: IO- + H2O2 -> H2O + O2 + I-What is the role of I- in this mechanism?A) catalystB) frequency factorC) intermediateD) transition state
Q:
The first-order isomerization reaction: cyclopropane → propene, has a rate constant of at 470C and an activation energy of 264 kJ/mol. What is the temperature of the reaction when the rate constant is equal to A) 126C
B) 411C
C) 510C
D) 540C
Q:
The first-order isomerization reaction: cyclopropane → propene, has a rate constant of at 470C and What is the activation energy, Ea, for the reaction?
A) 46 kJ/mol
B) 110 kJ/mol
C) 260 kJ/mol
D) 380 kJ/mol
Q:
The aquation of tris(1, 10-phenanthroline)iron(II) in acid solution takes place according to the equation:Fe(phen)32+ + 3 H3O+ + 3 H2O -> Fe(H2O)62+ + 3 phenH+.If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30C is 9.8 10-3 min-1, what is the rate constant at 50C?A) 4.4 10-4 min-1B) 2.2 10-1 min-1C) 4.6 100 min-1D) 2.3 103 min-1
Q:
The aquation of tris(1, 10-phenanthroline)iron(II) in acid solution takes place according to the equation:Fe(phen)32+ + 3 H3O+ + 3 H2O -> Fe(H2O)62+ + 3 phenH+If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30C is 9.8 10-3 min-1, what is the frequency factor, A?A) 2.4 10-24 min-1B) 2.4 10-20 min-1C) 5.2 1019 min-1D) 5.2 1023 min-1
Q:
The aquation of tris(1, 10-phenanthroline)iron(II) in acid solution takes place according to the equation:Fe(phen)32+ + 3 H3O+ + 3 H2O -> Fe(H2O)62+ + 3 phenH+If the activation energy is 126 kJ/mol and frequency factor is 8.62 1017 s-1, at what temperature is the rate constant equal to 3.63 10-3 s-1 for the first-order reaction?A) 0CB) 36CC) 50CD) 94C
Q:
The reaction for the decomposition of dinitrogen monoxide gas to form an oxygen radical is: . If the activation energy is 250 kJ/mol and the frequency factor is 8.0 1011 s-1, what is the rate constant for the first-order reaction at 1000 K?
A) 1.1 10-3 s-1
B) 7.0 10-2 s-1
C) 1.6 1013 s-1
D) 9.1 1024 s-1
Q:
The reaction for the decomposition of dinitrogen monoxide gas to form oxygen radicals is: . If the rate constant is 3.04 10-2 s-1 and the frequency factor is 8.00 1011 s-1, what is the activation energy for the first-order reaction at 700C?
A) 0.262 kJ/mol
B) 38.2 kJ/mol
C) 180 kJ/mol
D) 250 kJ/mol
Q:
Which part of the Arrhenius equation contains a term which measures the number of molecules that have the correct orientation for reaction?
A) activation energy
B) e-Ea/RT
C) frequency factor
D) none of these
Q:
Consider a bimolecular reaction in the gas phase. Which one of the following changes in condition will not cause an increase in the rate of the reaction?
A) add a catalyst
B) increase the temperature at constant volume
C) increase the volume at constant temperature
D) All of the above will increase the rate of reaction.
Q:
A common rule of thumb in organic chemistry is that increasing the temperature of a reaction at room temperature by 10C doubles the rate. Calculate Ea for a reaction that follows this rule of thumb. Assume room temperature is 25C.
A) 0.576 kJ
B) 12.2 kJ
C) 38.4 kJ
D) 52.9 kJ
Q:
When the temperature of a gas whose activation energy is 55 kJ/mol is increased from 300 K to 320 K, the fraction of collisions with sufficient energy to react
A) decreases by a factor of 2.
B) decreases by a factor of 4.
C) increases by a factor of 2.
D) increases by a factor of 4.
Q:
What fraction of collisions will have sufficient energy to react for a gas whose activation energy is 68 kJ/mol at 25C?
A) 1.2 10-12
B) 2.7 10-2
C) 0.96
D) 8.3 1011
Q:
The fraction of collisions with sufficient energy to react is equal to
A) A
B) Ea
C) e-Ea/RT
D) p
Q:
A gas molecule at 298 K and 1 atm pressure undergoes a collision with another gas molecule approximately every ________ seconds.
A) 10-15
B) 10-9
C) 10-6
D) 10-3
Q:
What factor affects the rate of a chemical reaction?
A) collision frequency
B) fraction of collisions with sufficient energy
C) orientation of molecules
D) all of the above
Q:
What is the minimum energy barrier that must be overcome for a chemical reaction to occur?
A) activation energy
B) net energy
C) potential energy
D) rate limiting energy
Q:
A gaseous reaction occurs by a two-step mechanism, shown below.Step 1: AX +Y2 AXY2 fastStep 2: AXY2 + AX -> 2 AXY slowIncluding concentration of only reactants and products, what is the rate law for this reaction?A) Rate = k[AX][Y2]B) Rate = k[AXY2]/[AX][Y2]C) Rate = k[AX]2[Y2]D) Rate = k[AXY]2/[AXY2][AX]
Q:
When the concentration of A is doubled, the rate for the reaction: quadruples.When the concentration of B is doubled the rate remains the same. Which mechanism below is consistent with the experimental observations?A) Step 1: A + B D (fast equilibrium)Step 2: A + D -> 2 C (slow)B) Step 1: A + B -> D (slow)Step 2: A + D 2 C (fast equilibrium)C) Step 1: 2 A -> D (slow)Step 2: B + D -> E (fast)Step 3: E -> 2 C (fast)D) Step 1: 2 A D (fast equilibrium)Step 2: B + D -> E (slow)Step 3: E -> 2 C (fast)
Q:
A three-step mechanism has been suggested for the formation of carbonyl chloride:Step 1: Cl2 ->2 Cl (fast, equilibrium)Step 2: Cl + CO -> COCl (fast, equilibrium)Step 3: COCl + Cl2 -> COCl2 + Cl (slow)What is the molecularity of the rate-determining step?A) unimolecularB) bimolecularC) termolecularD) none of these
Q:
What is the rate law for the elementary reaction shown below?2 HI -> H2 + I2A) Rate = k[HI]B) Rate = k[HI]2C) Rate = k[H2][I2]D) Rate = k[H2][I2]/[HI]2
Q:
Which general rate law below corresponds to an elementary bimolecular reaction?
A) Rate = k[A]
B) Rate = k[A][B][C]
C) Rate = k[A]2[B]
D) Rate = k[A][B]
Q:
Which of the following statements are true about reaction mechanisms?
I. A rate law can be written from the molecularity of the slowest elementary step.
II. The final rate law can include intermediates.
III. The rate of the reaction is dependent on the fastest step in the mechanism.
IV. A mechanism can never be proven to be the correct pathway for a reaction.
A) I, II, III
B) II, IV
C) I, III
D) I, IV
Q:
The slowest step in a reaction mechanism is called the ________ step.
A) activation
B) elementary
C) rate law
D) rate-determining
Q:
A three-step mechanism has been suggested for the formation of carbonyl chloride:Step 1: Cl2 -> 2 ClStep 2: Cl + CO -> COClStep 3: COCl + Cl2 -> COCl2 + ClWhich species is an intermediate in the mechanism?A) ClB) COC) COClD) COCl2
Q:
A mechanism for a naturally occurring reaction that destroys ozone is:Step 1: O3(g) + HO(g) -> HO2(g) + O2(g)Step 2: HO2(g) + O(g) -> HO(g) + O2(g)What is the molecularity of the overall reaction?A) unimolecularB) bimolecularC) none of these because molecularity is the difference of the exponents in the rate lawD) none of these because molecularity only refers to elementary steps
Q:
The decomposition of ozone in the stratosphere can occur by the following two-step mechanism:Step 1: Br + O3 ->BrO + O2Step 2: BrO + O -> Br + O2Which species is an intermediate in this mechanism?A) BrB) BrOC) OD) O3
Q:
A mechanism for a naturally occurring reaction that destroys ozone is:Step 1: O3(g) + HO(g) -> HO2(g) + O2(g)Step 2: HO2(g) + O(g) -> HO(g) + O2(g)Which species is an intermediate?A) HOB) HO2C) OD) O3
Q:
The elementary reaction: 2 HI -> H2 + I2, is an example of a ________ reaction.A) unimolecularB) bimolecularC) termolecularD) tetramolecular
Q:
The elementary reaction representing the formation of ozone: is an example of a ________ reaction.
A) unimolecular
B) bimolecular
C) termolecular
D) tetramolecular
Q:
Which statement below regarding the half-life of a zeroth-order reaction is true?
A) Each half-life is half as long as the preceding half-life.
B) Each half-life is twice as long as the preceding half-life.
C) Each half-life is four times as long as the preceding half-life.
D) The half-life remains unchanged throughout the course of the reaction.
Q:
For the zeroth-order reaction: A -> products, what will happen to the rate of reaction if the concentration of A is doubled?A) The rate will be halved.B) The rate will be doubled.C) The rate will be quadrupled.D) The rate will remain the same.
Q:
For the zeroth-order reaction: C -> products, -[C]/t = k, which of the following graphs would be expected to give a straight line?A) [C] vs. tB) ln[C] vs. tC) 1/[C] vs. tD) [C]2 vs. t
Q:
If the units for rate are M s-1, what are the units for the rate constant, k, for a zeroth-order reaction?
A) s-1
B) M-1
C) M s-1
D) M-1 s-1
Q:
For the hypothetical second order reaction: A ->products, the general rate law is: rate = k[A]2. How long is the third half-life of the reaction if [A]0 is 0.080 M and the first half-life is 22 minutes?A) 0.57 minB) 1.7 minC) 7.3 minD) 88 min
Q:
Which statement below regarding the half-life of a second-order reaction is true?
A) Each half-life is half as long as the preceding one.
B) Each half-life is twice as long as the preceding one.
C) Each half-life is four times as long as the preceding one.
D) The length of the half-life remains unchanged throughout the course of the reaction.
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:
Hydrogen iodide decomposes at 800 K via a second-order process to produce hydrogen and iodine according to the following chemical equation.2HI(g) -> H2(g) + I2(g)At 800 K it takes 142 seconds for the initial concentration of HI to decrease from 6.75 10-2 M to 3.50 10-2 M. What is the rate constant for the reaction at this temperature?A) 5.12 10-4 M-1s-1B) 9.69 10-2 M-1s-1C) 10.3 M-1s-1D) 1.95 103 M-1s-1
Q:
Nitrogen dioxide decomposes at 300C via a second-order process to produce nitrogen monoxide and oxygen according to the following chemical equation.2 NO2(g) ->2 NO(g) + O2(g).A sample of NO2(g) is initially placed in a 2.50-L reaction vessel at 300C. If the half-life and the rate constant at 300C are 11 seconds and 0.54 M-1 s-1, respectively, how many moles of NO2 were in the original sample?A) 0.17 molB) 0.42 molC) 5.9 molD) 15 mol
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:
Recent nuclear reactor accidents have contaminated many soils around the world. One of the isotopes deposited in soils is cesium-137. If the activity must fall by a factor of for contamination to disappear, how long will it take before uncontaminated crops may be grown in these soils? The half-life of cesium-137 is 30.2 years.
A) 301 years
B) 0.23 year
C) 33.1 years
D) 0.03 year
Q:
Iodine-131 is one of the many radioactive isotopes resulting from nuclear bomb explosions. How long would it take for 99% of the iodine-131 produced a nuclear explosion to disappear? The half-life of iodine-131 is 8.02 days.
A) 53.3 days
B) 80.2 days
C) 40.7 days
D) 802 days
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:
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 rate constant, k, for a first-order reaction is equal to 4.2 10-4 s-1. What is the half-life for the reaction?
A) 2.9 10-4 s
B) 1.2 103 s
C) 1.7 103 s
D) 2.4 103 s
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 to 0.46 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 at 1000 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 at 593 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/M2sB) 1.3 10-7 1/M2sC) 1.4 10-5 1/M2sD) 1.3 10-4 1/M2s
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 OCl-?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