HW08 - Kinetics

Question 10.5 pts

Consider the reaction:

2O3(g) 3O2(g)            rate = k[O3]2[O2]-1

What is the overall order of the reaction and the order with respect to [O3]?

  1. 2 and 2
  2. -1 and 3
  3. 3 and 2
  4. 1 and 2

Question 20.5 pts

When the reaction below:

3NO(g) N2O(g) + NO2(g)

is proceeding under conditions such that 0.015 mol/L of N2O is being formed each second, the rate of the overall reaction is ________ and the rate of change for NO is ________.

  1. 0.030 M/s; -0.005 M/s
  2. 0.015 M/s; -0.045 M/s
  3. 0.015 M/s; -0.005 M/s
  4. 0.015 M/s; 0.045 M/s

Question 31.0 pts

What is the rate law for the reaction below:

A + B + C D

if the following data were collected?

Exp [A]0 [B]0 [C]0 Initial Rate
1 0.4 1.2 0.7 2.32x10-3
2 1.3 1.2 0.9 7.54x10-3
3 0.4 4.1 0.8 9.25x10-2
4 1.3 1.2 0.2 7.54x10-3
  1. rate = 4.48x10-3 [A] [B]2 [C]
  2. rate = 5.37x10-3 [A] [B]3
  3. rate = 1.49x10-3 [B]3 [C]
  4. rate = 1.79x10-3 [B]2 [C]
  5. rate = 3.36x10-3 [A] [B]3

Question 41.0 pts

A chemical reaction is expressed by the balanced chemical equation:

A + 2B C

Consider the data below:

exp [A]0 [B]0 initial rate (M/min)
1 0.15 0.15 0.00110363
2 0.15 0.3 0.0044145
3 0.3 0.3 0.008829

 

Find the rate law for the reaction.

  1. rate = k [A] [B]2
  2. rate = k [B]2
  3. rate = k [A] [B]
  4. rate = k [A]2 [B]

Question 50.5 pts

Calculate the value of the rate constant (k) for the reaction in question 4.
  1. 0.00736
  2. 0.327
  3. 0.000166
  4. 0.00110

Question 60.5 pts

If the initial concentrations of both A and B are 0.31 M for the reaction in questions 4 and 5, at what initial rate is C formed?
  1. 0.0314 M/min
  2. 0.00974 M/min
  3. -0.00974 M/min
  4. 0.101 M/min

Question 71.0 pts

We know that the rate expression for the reaction below:

2NO + O2 2NO2

at a certain temperature is rate = [NO]2 [O2]. We carry out two experiments involving this reaction at the same temperature, but in the second experiment the initial concentration of NO is doubled while the initial concentration of O2 is halved. The initial rate in the second experiment will be how many times that of the first?

  1. 1
  2. 2
  3. 4
  4. 8

Question 81.0 pts

Consider the data collected for a chemical reaction between compounds A and B that is first order in A and first order in B:

rxn [A]0 [B]0 rate (M/s)
1 0.2 0.05 0.1
2 ? 0.05 0.4
3 0.4 ? 0.8

 

From the information above for 3 experiments, determine the missing concentrations of A and B. Answers should be in the order [A] then [B].

  1. 0.20 M; 0.80 M
  2. 0.80 M; 0.20 M
  3. 0.80 M; 0.10 M
  4. 0.40 M; 0.10 M
  5. 0.40 M; 0.20 M

Question 90.5 pts

For a reaction that is zero-order overall...
  1. the rate constant is zero.
  2. the activation energy is zero.
  3. the reactant concentration does not change with time.
  4. the rate does not change during the reaction.

Question 100.5 pts

Consider the reaction below:

A + B C

If it is 1st order in A and 0th order in B, a plot of ln[A] vs time will have a slope that is...

  1. decreasing exponentially.
  2. slowly increasing.
  3. increasing exponentially.
  4. constant.

Question 111.0 pts

Consider the reaction below:

H2CO3(aq) CO2(aq) + H2O(l)

If it has a half-life of 1.6 sec, how long will it take a system with [H2CO3]0 of 2M to reach [H2CO3] of 125mM?

  1. 6.4 sec
  2. Not enough information is given.
  3. 2.9 sec
  4. 3.2 sec

Question 121.0 pts

At a certain fixed temperature, the reaction below:

A(g) + 2B(g) AB2(g)

is found to be first order in the concentration of A and zeroth order in the concentration of B. The reaction rate constant is 0.05s-1. If 2.00 moles of A and 4.00 moles of B are placed in a 1.00 liter container, how many seconds will elapse before the concentration of A has fallen to 0.30 moles/liter?

  1. There is not enough information to answer.
  2. 10.22 sec
  3. 2.83 sec
  4. 37.94 sec

Question 130.5 pts

The reaction below:

A products

is observed to obey first-order kinetics. Which of the following plots should give a straight line?

  1. ln[A] vs t-1
  2. [A] vs t
  3. [A] vs t-1
  4. ln[A] vs k-1
  5. [A] vs k
  6. ln[A] vs t
  7. ln[A] vs k

Question 141.0 pts

For the reaction below:

cyclobutane(g) 2ethylene(g)

at 800K, a plot of ln[cyclobutane] vs t gives a straight line with a slope of -1.6 s-1. Calculate the time needed for the concentration of cyclobutane to fall to 1/16 of its initial value.

  1. 1.3 sec
  2. 0.63 sec
  3. 1.6 sec
  4. 1.7 sec

Question 151.0 pts

The initial concentration of the reactant A in a first-order reaction is 1.2 M. After 69.3 sec, the concentration has fallen to 0.3 M. What is the rate constant k?
  1. not enough information
  2. 0.02 s-1
  3. 0.01 s-1
  4. 0.2 s-1

Question 161.0 pts

A reaction is found to be first order with respect to one of the reactant species, A. When might a plot of ln[A] vs time NOT yield a straight line?
  1. when the rate also depends on the concentration of another reactant as well
  2. All of the other answers could be correct.
  3. if the reaction comes to equilibrium
  4. if the reaction has any significant backward rate

Question 170.5 pts

Consider the following elementary reactions:

a) NO + O3  NO2 + O2

b) CS2  CS + S

c) O + O2 + N2  O3 + N2

Identify the molecularity of each reaction respectively.

  1. all three elementary reactions are bimolecular
  2. tetramolecular, termolecular, pentamolecular
  3. it is impossible to know without knowing the overall reaction for each
  4. bimolecular, unimolecular, termolecular

Question 181.0 pts

A and B react to form C according to the single step reaction below:

A + 2B  C

Which of the following is the correct rate equation for [B] and the correct units for the rate constant of this reaction?

  1. \frac{\Delta\left[B\right]}{\Delta t}\:=\:-2k\left[A\right]\left[B\right]^2;\:\:\:\frac{1}{M^2\cdot s}
  2. \frac{\Delta\left[B\right]}{\Delta t}\:=\:-2k\left[A\right]\left[B\right];\:\:\:\frac{1}{M\cdot s}
  3. \frac{\Delta\left[B\right]}{\Delta t}\:=\:-\frac{2k\left[A\right]\left[B\right]}{\left[C\right]};\:\:\:\frac{1}{M\cdot s}
  4. \frac{\Delta\left[B\right]}{\Delta t}\:=\:-k\left[A\right]\left[B\right]^2;\:\:\:\frac{1}{M^2}

Question 191.0 pts

Consider the mechanism below:

NO2 + F2  NO2F + F            k1, slow

F + NO2  NO2F                    k2, fast

What is the rate law?

  1. rate = k1[NO2F][F2]
  2. rate = k1k2[NO2]2
  3. rate = k2[NO2]2
  4. rate = k1[NO2][F2]
  5. rate = k2[NO2][F]

Question 201.0 pts

Determine the overall balanced equation for a reaction having the following proposed mechanism:

Step 1:   B2 + B2  E3 + D          slow

Step 2:   E3 + A  B2 + C2          fast

and write an acceptable rate law.

  1. A + B2  C2 + D; rate = k[B2]2
  2. A + B2  C2 + D; rate = k[A][B2]
  3. E3 + A  B2 + C2; rate = k[E3][A]
  4. 2B2  E3 + D; rate = k[B2]2

Question 211.0 pts

Consider the reaction below:

H2(g) + I2(g)  2HI(g)

The proposed mechanism of this reaction is:

I2 ⇌ 2I                          k1, k-1(reverse rxn), fast

2I + H2  2HI          k2, slow

What is the rate of the overall reaction?

  1. rate\:=\:k_1k_2\left[I_2\right]\left[H_2\right]
  2. rate\:=\:\frac{k_{-1}k_2}{k_1}\left[I_2\right]\left[H_2\right]
  3. rate\:=\:\frac{k_1k_2}{k_{-1}}\left[I_2\right]\left[H_2\right]
  4. rate\:=\:k_2\left[I\right]^2\left[H_2\right]
  5. rate\:=\:\frac{k_1k_2}{k_{-1}}\left[I\right]^2\left[H_2\right]

Question 221.0 pts

A reaction rate increases by a factor of 655 in the presence of a catalyst at 37°C. The activation energy of the original pathway is 106 kJ/mol. What is the activation energy of the new pathway, all other factors being equal?
  1. 89.3 J/mol
  2. 16,600 J/mol
  3. 16,600 kJ/mol
  4. 89.3 kJ/mol

Question 231.0 pts

A given reaction has an activation energy of 24.52 kJ/mol. At 25°C, the half-life is 4 minutes. At what temperature will the half-life be reduced to 20 seconds?
  1. 100°C
  2. 150°C
  3. 115°C
  4. 125°C

Question 241.0 pts

For the reaction below:

HO(g) + H2(g) \longrightarrow H2O(g) + H(g)

a plot of lnK vs 1/T gives a straight line with a slope equal to -5.1x103 K. What is the activation energy for this reaction?

  1. 12 kJ/mol
  2. 42 kJ/mol
  3. 5.1 kJ/mol
  4. 98 kJ/mol

Question 251.0 pts

A certain reaction has an activation energy of 0.8314 kJ/mol and a rate constant of 2.718 s-1 at -73°C. At -173°C, which expression for the rate constant is correct?
  1. ln(k2) = 1
  2. ln(k2) = 0.5
  3. ln(k2) = -0.5
  4. ln(k2) = 1.5

Question 261.0 pts

A food substance kept at 0°C becomes rotten (as determined by a good quantitative test) in 8.3 days. The same food rots in 10.6 hours at 30°C. Assuming the kinetics of the microorganisms enzymatic action is responsible for the rate of decay, what is the activation energy for the decomposition process? Hint: Rate varies INVERSELY with time; a faster rate produces a shorter decomposition time.
  1. 0.45 kJ/mol
  2. 23.4 kJ/mol
  3. 2.34 kJ/mol
  4. 67.2 kJ/mol

Question 271.0 pts

A catalyst...
  1. speeds up the reaction and increases K to favor product formation.
  2. increases K to favor product formation.
  3. speeds up the reaction but does not change K.
  4. changes the reaction mechanism to ensure that K is increased.

Question 281.0 pts

All else being equal, a reaction with a higher activation energy compared to one with a lower activation energy will...
  1. be more exothermic.
  2. be more endothermic.
  3. proceed faster.
  4. proceed slower.

Question 291.0 pts

Consider the potential energy diagram below:

EndoVsExoRxnCoor.png

What is the change in enthalpy (\Delta H) for the reaction A \longrightarrow B?

  1. -100 kJ
  2. 350 kJ
  3. -350 kJ
  4. 100 kJ

Question 301.0 pts

Consider the potential energy diagram in the previous question where A reacts to form B. What is the activation energy (Ea) for the reaction?
  1. 200 kJ
  2. 250 kJ
  3. 100 kJ
  4. 350 kJ

Question 311.0 pts

Which of the following statements is TRUE?
  1. The exponents in the rate-law must match the coefficients in the balanced chemical equation for the reaction.
  2. If the exponents in the rate-law do not match the coefficients in the balanced equation, then we know that the reaction does not take place in one step.
  3. The rate-law for a reaction can be predicted from the balanced chemical equation.
  4. If the exponents in the rate-law do not match the coefficients in the balanced chemical equation, then we know that the reaction takes place in one step.

Question 321.0 pts

"Reaction mechanisms usually involve only unimolecular or bimolecular steps."

Is this statement true or false?

  1. True, because collisions of higher molecularity would occur too infrequently to account for an observed rate.
  2. False.
  3. True, because steps of higher molecularity would not be compatible with observed reaction rate laws.
  4. True, because the activation energy for collisions of higher molecularity would be too great.

Question 331.0 pts

Which of the following is/are ALWAYS true concerning collision and transition state theory?

I) Transition states are short-lived.

II) A balanced reaction shows which species must collide for the reaction to occur.

III) Intermediates are short-lived.

  1. II and III
  2. II only
  3. I only
  4. III only
  5. All are true.
  6. I and III

Question 341.0 pts

Consider the following reaction mechanism:

1) Cl2 + Pt \longrightarrow 2Cl + Pt

2) Cl + CO + Pt \longrightarrow ClCO + Pt

3) Cl + ClCO \longrightarrow Cl2CO

Overall: Cl2 + CO \longrightarrow Cl2CO

Which species is/are intermediates?

  1. Pt, Cl
  2. ClCO
  3. Pt, Cl, ClCO
  4. Cl, ClCO
  5. Pt













CH302 · 50520 Principles of Chemistry II


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