Question 1

Substitute natural gas can be synthesized by passing carbon monoxide and hydrogen over Ni or Co at 400°C.   This process is an example of homogeneous catalysis.

Accepted Answer

A) True 
 B)False

Question 2

The reaction A + 2B $\rarr$ products has the rate law, rate = k[A][B]3.If the concentration of B is doubled while that of A is unchanged, by what factor will the rate of reaction increase?

Accepted Answer

A) 2 
B) 4 
C) 6 
D) 8 
E) 9 
A) 2 
B) 4 
C) 6 
D) 8 
E) 9

Question 3

The gas phase reaction of nitrogen dioxide and carbon monoxide was found experimentally to be second-order with respect to NO2, and zero-order with respect to CO below 25°C. NO2 + CO $\rarr$ NO + CO2
 Which one of the following mechanisms is consistent with the observed reaction order?

Accepted Answer

A) NO2 + 2CO   N + 2CO2 fast N + NO2 $\rarr$ 2NO slow 
B) NO2 + 2CO $\rarr$N + 2CO2 slow N + NO2 $\rarr$ 2NO fast 
C) NO2 + NO2 $\rarr$ NO3 + NO fast NO3 + CO $\rarr$NO2 + CO2 slow 
D) NO2 + NO2 $\rarr$ NO3 + NO slow NO3 + CO $\rarr$NO2 + CO2 fast 
A) NO2 + 2CO   N + 2CO2 fast N + NO2 $\rarr$ 2NO slow 
B) NO2 + 2CO $\rarr$N + 2CO2 slow N + NO2 $\rarr$ 2NO fast 
C) NO2 + NO2 $\rarr$ NO3 + NO fast NO3 + CO $\rarr$NO2 + CO2 slow 
D) NO2 + NO2 $\rarr$ NO3 + NO slow NO3 + CO $\rarr$NO2 + CO2 fast

Question 4

When acetaldehyde at a pressure of 364 mmHg is introduced into an evacuated 500.mL flask at 518°C, the half-life for the second-order decomposition process, CH3CHO $\rarr$ CH4 + CO, is 410.s.What will the total pressure in the flask be after 1.00 hour?

Accepted Answer

A) 327 mmHg 
B) 654 mmHg 
C) 37 mmHg 
D) 691 mmHg 
E) 728 mmHg 
A) 327 mmHg 
B) 654 mmHg 
C) 37 mmHg 
D) 691 mmHg 
E) 728 mmHg

Question 5

A nuclear stress test utilizes a gamma-emitting radioisotope such as thallium-201 to follow the flow of blood through the heart - first at rest, and then under stress.The first-order rate constant for the decay of thallium-201 is 9.5 x 10-3 hr-1.Calculate how long it takes for the amount of thallium-201 to fall to 5.0% of its original value.

Accepted Answer

Question 6

An increase in the temperature of the reactants causes an increase in the rate of reaction.The best explanation for this behavior is that as the temperature increases,

Accepted Answer

A) the concentration of reactants increases. 
B) the activation energy decreases. 
C) the collision frequency increases. 
D) the fraction of collisions with total kinetic energy greater than Ea increases. 
E) the activation energy increases. 
A) the concentration of reactants increases. 
B) the activation energy decreases. 
C) the collision frequency increases. 
D) the fraction of collisions with total kinetic energy greater than Ea increases. 
E) the activation energy increases.

Question 7

The reaction A + 2B $\rarr$ products has been found to have the rate law, rate = k[A] [B]2.While holding the concentration of A constant, the concentration of B is increased from x to 3x.Predict by what factor the rate of reaction increases.

Accepted Answer

A) 3 
B) 6 
C) 9 
D) 27 
E) 30 
A) 3 
B) 6 
C) 9 
D) 27 
E) 30

Question 8

It is possible for the following overall reaction to consist of a one step mechanism:
2A $\rarr$ products

Accepted Answer

A) True 
 B)False

Question 9

The rate constant for the first-order decomposition of C4H8 at 500°C is 9.2 × 10-3 s-1.How long will it take for 10.0% of a 0.100 M sample of C4H8 to decompose at 500°C?

Accepted Answer

Question 10

In general, to calculate the activation energy for an elementary step given the rate constants at two different temperatures, which equation should be used?

Accepted Answer

A) ln([A]t/[A]o)= - kt 
B) t1/2 = ln2/k 
C) ln(k1/k2)= Ea/R( (T1 - T2)/T1T2) 
D) 1/[A]t = kt + 1/[A]o 
E) Rate = k[A] 
A) ln([A]t/[A]o)= - kt 
B) t1/2 = ln2/k 
C) ln(k1/k2)= Ea/R( (T1 - T2)/T1T2) 
D) 1/[A]t = kt + 1/[A]o 
E) Rate = k[A]

Question 11

The thermal decomposition of acetaldehyde, CH3CHO $\rarr$CH4 + CO, is a second-order reaction.The following data were obtained at 518°C. 
  
Calculate the rate constant for the decomposition of acetaldehyde from the above data.

Accepted Answer

A) 2.2 × 10-3/s 
B) 0.70 mmHg/s 
C) 2.2 × 10-3/mmHg·s 
D) 6.7 × 10-6/mmHg·s 
E) 5.2 × 10-5/mmHg·s 
A) 2.2 × 10-3/s 
B) 0.70 mmHg/s 
C) 2.2 × 10-3/mmHg·s 
D) 6.7 × 10-6/mmHg·s 
E) 5.2 × 10-5/mmHg·s

Question 12

The rate determining step must be the first step of a reaction mechanism in all cases.

Accepted Answer

A) True 
 B)False

Question 13

A reaction was experimentally determined to follow the rate law, Rate = k[A] where k = 0.15 s-1.Starting with [A]o = 0.225M, how many seconds will it take for [A]t = 0.0350M

Accepted Answer

A) 3.4 x 10-2 s 
B) 5.3 x 10-3 s 
C) 12 s 
D) 160 s 
E) 1.3 s 
A) 3.4 x 10-2 s 
B) 5.3 x 10-3 s 
C) 12 s 
D) 160 s 
E) 1.3 s

Question 14

The first-order decomposition, A $\rarr$ products, has a rate constant of 0.150 s-1.Starting with [A]o = 0.350 M, how much time is required for [A]t = 0.125 M?

Accepted Answer

A) 6.86 s 
B) 2.98 s 
C) 34 s 
D) 1.50 s 
E) 4.62 s 
A) 6.86 s 
B) 2.98 s 
C) 34 s 
D) 1.50 s 
E) 4.62 s

Question 15

At 700 K, the rate constant for the following reaction is 6.2 × 10-4 min-1.   How many minutes are required for 20% of a sample of cyclopropane to isomerize to propene?

Accepted Answer

A) 1,120 min 
B) 360 min 
C) 3710 min 
D) 1.4 × 10-4 min 
E) 280 min 
A) 1,120 min 
B) 360 min 
C) 3710 min 
D) 1.4 × 10-4 min 
E) 280 min

Question 16

At a certain temperature, the data below were collected for the reaction below.
2ICl + H2 $\rarr$I2 + 2HCl.
Determine the rate constant for the reaction.

Accepted Answer

Question 17

For the overall chemical reaction shown below, which one of the following statements can be rightly assumed? 2H2S(g)+ O2(g)\9\rarr\) 2S(s)+ 2H2O(l)

Accepted Answer

A) The reaction is third-order overall. 
B) The reaction is second-order overall. 
C) The rate law is, rate = k[H2S]2 [O2]. 
D) The rate law is, rate = k[H2S] [O2]. 
E) The rate law cannot be determined from the information given. 
A) The reaction is third-order overall. 
B) The reaction is second-order overall. 
C) The rate law is, rate = k[H2S]2 [O2]. 
D) The rate law is, rate = k[H2S] [O2]. 
E) The rate law cannot be determined from the information given.

Question 18

Nitrous oxide (N2O)decomposes at 600°C according to the balanced equation 2N2O(g)$\rarr$2N2(g)+ O2(g)
A reaction mechanism involving three steps is shown below.Identify all of the catalysts in the following mechanism.
Cl2(g)$\rarr$ 2Cl(g)
N2O(g)+ Cl(g)$\rarr$N2(g)+ ClO(g)(occurs twice)
ClO(g)+ ClO(g)$\rarr$Cl2(g)+ O2(g)

Accepted Answer

A) Cl 
B) Cl2 
C) ClO 
D) N2O 
E) ClO and Cl 
A) Cl 
B) Cl2 
C) ClO 
D) N2O 
E) ClO and Cl

Question 19

The reaction C4H10 $\rarr$ C2H6 + C2H4 has an activation energy (Ea)of 350 kJ/mol, and the Ea of the reverse reaction is 260 kJ/mol.Estimate $\Delta$H, in kJ/mol, for the reaction as written above.

Accepted Answer

A) -90 kJ/mol 
B) +90 kJ/mol 
C) 350 kJ/mol 
D) -610 kJ/mol 
E) +610 kJ/mol 
A) -90 kJ/mol 
B) +90 kJ/mol 
C) 350 kJ/mol 
D) -610 kJ/mol 
E) +610 kJ/mol

Question 20

For the reaction BrO3- + 5Br-+ 6H+ $\rarr$ 3Br2 + 3H2O at a particular time, -$\Delta$[BrO3-]/$\Delta$t = 1.5 × 10-2 M/s.What is -$\Delta$[Br-]/$\Delta$t at the same instant?

Accepted Answer

A) 13 M/s 
B) 7.5 × 10-2 M/s 
C) 1.5 × 10-2 M/s 
D) 3.0 × 10-3 M/s 
E) 330 M/s 
A) 13 M/s 
B) 7.5 × 10-2 M/s 
C) 1.5 × 10-2 M/s 
D) 3.0 × 10-3 M/s 
E) 330 M/s

Exam 13: Chemical Kinetics

Substitute natural gas can be synthesized by passing carbon monoxide and hydrogen over Ni or Co at 400°C. This process is an example of homogeneous catalysis.

The reaction A + 2B →\rarr→ products has the rate law, rate = k[A][B]3.If the concentration of B is doubled while that of A is unchanged, by what factor will the rate of reaction increase?

The gas phase reaction of nitrogen dioxide and carbon monoxide was found experimentally to be second-order with respect to NO2, and zero-order with respect to CO below 25°C. NO2 + CO →\rarr→ NO + CO2 Which one of the following mechanisms is consistent with the observed reaction order?

When acetaldehyde at a pressure of 364 mmHg is introduced into an evacuated 500.mL flask at 518°C, the half-life for the second-order decomposition process, CH3CHO →\rarr→ CH4 + CO, is 410.s.What will the total pressure in the flask be after 1.00 hour?

An increase in the temperature of the reactants causes an increase in the rate of reaction.The best explanation for this behavior is that as the temperature increases,

The reaction A + 2B →\rarr→ products has been found to have the rate law, rate = k[A] [B]2.While holding the concentration of A constant, the concentration of B is increased from x to 3x.Predict by what factor the rate of reaction increases.

It is possible for the following overall reaction to consist of a one step mechanism: 2A →\rarr→ products

The rate constant for the first-order decomposition of C4H8 at 500°C is 9.2 × 10-3 s-1.How long will it take for 10.0% of a 0.100 M sample of C4H8 to decompose at 500°C?

In general, to calculate the activation energy for an elementary step given the rate constants at two different temperatures, which equation should be used?

The thermal decomposition of acetaldehyde, CH3CHO →\rarr→ CH4 + CO, is a second-order reaction.The following data were obtained at 518°C. Calculate the rate constant for the decomposition of acetaldehyde from the above data.

The rate determining step must be the first step of a reaction mechanism in all cases.

A reaction was experimentally determined to follow the rate law, Rate = k[A] where k = 0.15 s-1.Starting with [A]o = 0.225M, how many seconds will it take for [A]t = 0.0350M

The first-order decomposition, A →\rarr→ products, has a rate constant of 0.150 s-1.Starting with [A]o = 0.350 M, how much time is required for [A]t = 0.125 M?

At 700 K, the rate constant for the following reaction is 6.2 × 10-4 min-1. How many minutes are required for 20% of a sample of cyclopropane to isomerize to propene?

At a certain temperature, the data below were collected for the reaction below. 2ICl + H2 →\rarr→ I2 + 2HCl. Determine the rate constant for the reaction.

For the overall chemical reaction shown below, which one of the following statements can be rightly assumed? 2H2S(g)+ O2(g)\9\rarr\) 2S(s)+ 2H2O(l)

The reaction C4H10 →\rarr→ C2H6 + C2H4 has an activation energy (Ea)of 350 kJ/mol, and the Ea of the reverse reaction is 260 kJ/mol.Estimate Δ\DeltaΔ H, in kJ/mol, for the reaction as written above.

For the reaction BrO3- + 5Br-+ 6H+ →\rarr→ 3Br2 + 3H2O at a particular time, - Δ\DeltaΔ [BrO3-]/ Δ\DeltaΔ t = 1.5 × 10-2 M/s.What is - Δ\DeltaΔ [Br-]/ Δ\DeltaΔ t at the same instant?

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The reaction A + 2B $\rarr$ products has the rate law, rate = k[A][B]³.If the concentration of B is doubled while that of A is unchanged, by what factor will the rate of reaction increase?

The gas phase reaction of nitrogen dioxide and carbon monoxide was found experimentally to be second-order with respect to NO₂, and zero-order with respect to CO below 25°C. NO₂ + CO $\rarr$ NO + CO₂ Which one of the following mechanisms is consistent with the observed reaction order?

When acetaldehyde at a pressure of 364 mmHg is introduced into an evacuated 500.mL flask at 518°C, the half-life for the second-order decomposition process, CH₃CHO $\rarr$ CH₄ + CO, is 410.s.What will the total pressure in the flask be after 1.00 hour?

The reaction A + 2B $\rarr$ products has been found to have the rate law, rate = k[A] [B]².While holding the concentration of A constant, the concentration of B is increased from x to 3x.Predict by what factor the rate of reaction increases.

It is possible for the following overall reaction to consist of a one step mechanism: 2A $\rarr$ products

The rate constant for the first-order decomposition of C₄H₈ at 500°C is 9.2 × 10^-3 s^-1.How long will it take for 10.0% of a 0.100 M sample of C₄H₈ to decompose at 500°C?

A reaction was experimentally determined to follow the rate law, Rate = k[A] where k = 0.15 s^-1.Starting with [A]_o = 0.225M, how many seconds will it take for [A]_t = 0.0350M

The first-order decomposition, A $\rarr$ products, has a rate constant of 0.150 s^-1.Starting with [A]_o = 0.350 M, how much time is required for [A]_t = 0.125 M?

At 700 K, the rate constant for the following reaction is 6.2 × 10^-4 min^-1. How many minutes are required for 20% of a sample of cyclopropane to isomerize to propene?

For the overall chemical reaction shown below, which one of the following statements can be rightly assumed? 2H₂S(g)+ O₂(g)\9\rarr\) 2S(s)+ 2H₂O(l)

The reaction C₄H₁₀ $\rarr$ C₂H₆ + C₂H₄ has an activation energy (E_a)of 350 kJ/mol, and the E_a of the reverse reaction is 260 kJ/mol.Estimate $\Delta$ H, in kJ/mol, for the reaction as written above.

For the reaction BrO₃^-+ 5Br^-+ 6H⁺ $\rarr$ 3Br₂ + 3H₂O at a particular time, - $\Delta$ [BrO₃^-]/ $\Delta$ t = 1.5 × 10^-2 M/s.What is - $\Delta$ [Br^-]/ $\Delta$ t at the same instant?