Full Name: ________________
Date: ________________
Chem 4U- Thermodynamics & Kinetics Test
Multiple Choice (K/U)
Identify the letter of the choice that best completes the statement or answers the question.
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1. A chemical system in which both energy and matter can flow into or out of a system is described as
a. a closed system
d. a chemical system
b. an open system
e. none of the above
c. an isolated system
2. A chemical system in which matter cannot flow into or out of a system is described as
a. a closed system
d. a chemical system
b. an open system
e. none of the above
c. an isolated system
3. An enthalpy change is
a. the difference in the kinetic energy of the reactants and the products in a chemical change
b. the difference in the potential energy of the reactants and the products in a chemical change
c. the sum of the potential and kinetic energies of the reactants and products
d. the sum of the potential and kinetic energies of the products
e. the sum of the potential and kinetic energies of the reactants
4. Which statement concerning the Law of Conservation of Energy is not true?
a. it applies to all chemical changes
b. it involves all different forms of energy
c. it applies to nuclear reactions
d. it includes potential energy
e. it involves heat content of substances
5. What is another way to write the following equation?
C2H6(g)  C2H2(g) + 2H2(g) ΔH = 3.2  102 kJ/mol
a. C2H6(g)  C2H6(g) + 2H2(g) + 3.2  102 kJ
b. C2H6(g) + 3.2  102 kJ  C2H2(g) + 2H2(g)
c. 2H2(g) + C2H2(g) + 3.2  102 kJ  C2H6(g)
d. C2H6(g) – 3.2  102 kJ  C2H2(g) + 2H2(g)
e. none of the above
6. Consider the following four equations:
1. C6H6(l) + 15/2 O2(g)  6CO2(g) + 3H2O(l) )H1
2. H2(g) + 1/2 O2(g)  H2O(l) H2
3. C(s) + O2(g)  CO2(g) H3
4. 6C(s) + 3H2(g)  C6H6(l) H4
The enthalpy change for reaction 1, H1 can be obtained by combining the H's for the other reactions in which of the
following ways?
a. 6(H3) + 3(H2) + H4
d. 6(H3) + 3(H2) – H4
b. 6(H3) – 3(H2) + H4
e. none of the above
c. 6(H3) – 3(H2) + H4
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7. NaCl(s) + H2O(l)  NaCl(aq) H = +1.67 kJ/mol of NaCl (at 298 K)
If sufficient NaCl is dissolved in water to form 1.00 L of 2.00 mol/L NaCl solution, the change in enthalpy of
the system will be
a. 1.67 kJ
d. 2.50 kJ
b. 3.34 kJ
e. none of the above
c. 8.35 kJ
8. Using the standard heats of formation, what is the enthalpy change per mole of CO2 for the following
reaction?
CO(g) + 1/2 O2(g)  CO2(g)
a. –506 kJ
b. –284 kJ
c. +284 kJ
d. +506 kJ
e. –617 kJ
2
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9. Based on the heat of formation of MgO, how much energy is required to decompose 48.6 g of MgO?
a. 603 kJ
d. 60.3 kJ
b. 725 kJ
e. 1504 kJ
c. 301 kJ
10. Which of the following equations represents the correct heat of formation of water vapour?
a. H2(g) + 1/2 O2(g)  H2O(l)
d. H2(g) + O2(g)  2H2O(g)
b. H2(g) + O(g)  H2O(g)
e. H2(g) + 1/2 O2(g)  H2O(g)
c. 2H(g) + O(g)  H2O(g)
11. What property would be appropriate to measure the reaction rate in the following reaction:
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a. change in conductivity
d. change in pressure
b. change in mass
e. change in volume
c. change in colour
12. What property would be appropriate to measure the reaction rate in the following reaction:
a. change in conductivity
d. change in pressure
b. change in mass
e. change in temperature
c. change in colour
13. A catalyst is only effective if it
a. is present in large quantities
b. is added before the reactants come in contact with each other
c. is specific to the particular reaction
d. is heated before it is added to the reaction
e. all of the above
14. According to the Rate Law, the rate (r) for the reaction
a. [X]
d.
b.
[Y]
c.
[products]
must be proportional to
e.
15. If for the reaction,
, the rate law is determined to be
reaction is which of the following?
a. 1
d. 4
b. 2
e. 5
c. 3
16. The following graph represents a reaction of order
a. 0
d. 3
b. 1
e. 4
c. 2
17. Ineffective collisions are collisions that involve particles
a. without enough energy to react
b. with the wrong orientation
c. that rebound from the collision unchanged
d. that cannot react
e. all of the above
, then the order of the
3
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18. The rate determining step is
a. the first step in a reaction mechanism
b. the last step in a reaction mechanism
c. the slowest step in a reaction mechanism
d. the fastest step in a reaction mechanism
e. the only step in a reaction mechanism
19. Reaction intermediates are
a. steps within a reaction mechanism
b. the step that determines the rate of the reaction
c. products formed in the overall equation
d. products formed within some steps of the reaction mechanism
e. none of the above
Short Answer (I/C) – 3 marks each
20. Dry ice is solid carbon dioxide. It does not melt, but instead it sublimes directly to the gas state.
a. Is this change endothermic or exothermic? ______________________
b. What sign would the
have? __________________
c. Explain the transfer of energy involved in this change.
21. A kilogram of water and a kilogram of sand are at the same temperature. Do the two substances contain the
same amount of heat energy? Explain.
22. How can a graph of
versus [A] can be used to determine the order of the reaction?
23. What is meant by the activation energy of the reaction?
24. If an iron ring with a mass of 5.5 g changes temperature from 25.0ºC to 28.0ºC, how much energy has it
absorbed? ciron=0.444 J/g·˚C
25. 7.28 kJ of heat is released when 40.0 g of Br2 (bromine) vapour at 332 K condense to a liquid. What is the
molar heat of vaporization of Br2?
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26. Consider the following equation for the combustion of H2(hydrogen):
H2(g) + 1/2O2(g)  H2O(g) + 243 kJ
In order to produce 972 kJ of heat, how many grams of H2 must burn?
27. Ethanol, C2H5OH, is made industrially by the reaction of water with ethylene, C2H44. Calculate the value of
Ho for the reaction
C2H4(g) + H2O(l)  C2H5OH(l)
given the following thermochemical equations:
C2H4(g) + 3 O2(g)  2 CO2(g) + 2 H2O(l) Ho = –1411.1 kJ
C2H5OH(l) + 3 O2(g)  2 CO2(g) + 3 H2O(l) Ho = –1367.1 kJ
28. The thermite reaction is quite a common reaction and is spectacular. Iron (III) oxide and metallic aluminum
produce iron and aluminum oxide in a few seconds:
Find H for this reaction given the following information.
29. Consider the decomposition of hydrogen peroxide as shown below. If the rate of decomposition of hydrogen
peroxide at a particular temperature is determined to be 0.098 mol/(L·s), what are the rates of reaction with
respect to each of the two products of the decomposition reaction?
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30.
Use the following data to calculate the reaction rate law for the system. (note: the “rate law” is the
“rate law expression” together with the appropriate value of k. Hint: find k while solving).
(there is space on next page)
Experiment
NO (mol/L)
H2 (mol/L)
Initial Rate of Reaction (mol/(L·s))
1
0.001
0.004
0.002
2
0.002
0.004
0.008
3
0.003
0.004
0.018
4
0.004
0.001
0.008
5
0.004
0.002
0.016
6
0.004
0.003
0.024
31. The chemical reaction between X and Y is known to be first order for each reactant. Find the unknown
information in the table below. (hint: find “k” first)
Experiment
[A] (mol/L)
[B] (mol/L)
1
Rate
(mol/L·s)
0.20
0.10
0.40
2
0.80
? (a)
0.40
3
1.60
0.20
? (b)
M.C.
Short Ans.
K/U
I, C
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*** marked by: (first & last name):
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Chem4U-Thermo,Kinetics
Answer Section
MULTIPLE CHOICE
1B
2A
3A
4C
5B
6D
7B
8B
9B
10 E
11 C
12 D
13 C
14 E
15 C
16 C
17 E
18 C
19 D
SHORT ANSWER
20. ANS:
a. endothermic
b. positive
c. the energy required for the reaction would be taken from the air surrounding the dry ice
as particles from the air collide with the dry ice, energy would be passed to the ice causing it to sublime
21. ANS: No. Since the water and sand have very different heat capacities, they would contain significantly
different amounts of heat energy.
22. ANS:
- when a series of kinetics experiments is performed on a given system, the rates of reaction (
) are
measured for different initial concentrations of a reactant.
- when the evidence is graphed, you may see one or more of these results
zero-order reaction
first order reaction
greater than first order reaction
23. ANS: the activation energy of the reaction is the minimum increase in potential energy of a system required
for molecules to react
24. ANS:
m=
c=
T =
=
q=
=
=
5.5 g
0.444 J/gºC
28.0ºC – 25.0ºC
3.0ºC
mcT
(5.5 g)(0.444 J/gºC)(3.0ºC)
7.3 J
7.3 J of energy has been absorbed.
25. ANS:
Calculate the number of moles of Bromine
Calculate the molar enthalpy
The molar heat of vaporization of Br2 is 29.1
kJ/mol.
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26. ANS:
Determine the number of moles of H2 that are
required.
Calculate the mass of H2 required
8.08 g of H2 would need to be burned.
27. ANS: Show the addition of equations to give "target" reaction
C2H4(g) + 3 O2(g)  2 CO2(g) + 2 H2O(l)
Ho = –1411.1 kJ
2 CO2(g) + 3 H2O(l)  C2H5OH(l) + 3 O2(g)
Ho = +1367.1 kJ
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C2H4(g) + H2O(l)  C2H5OH(l)
Ho = –44 kJ
The Ho for the reaction is 44 kJ.
28. ANS: Determine equation for thermite reaction:
Rearrange given equations to add to add to target equation
The H the reaction is –848 kJ.
ALTERNATIVELY, YOU MIGHT REALIZE THAT THE REVERSE OF THE 2ND EQUATION IS
THE HEAT OF FORMATION OF Fe2O3, AND THEN USE -822kJ/mol AND THIS EQUATION:
29.
ANS: Write a balanced equation for the reaction
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The rate of production of water is 0.098 mol/(L·s) and the production of oxygen gas is 0.049 mol/(L·s).
30. ANS: From the equation we can write the partial rate law as
Using experiments 1 and 2, the concentration jumps from 0.001 to 0.002 moles/L. IT DOUBLES!! The rates
for these same experiments. The rate jumps from 0.002 to 0.008 moles/L seconds. IT QUADRUPLED!!.
The exponential constant 'm' for the [NO] is the mathematical relationship between these two values. i.e.
2m = 4 therefore m = 2 because 22 = 4
Look at experiments 4 and 5. The H2 concentration DOUBLES and the rate DOUBLES.
2n = 2 therefore n = 1 since 21 = 2
So the rate law expression can be rewritten as
rate = k [NO]2 [H2]1
Now to determine the value of 'k'. Choose any one of the experiments.
Using experiment 1. Using the rate law, above fill in the values from the data table.
0.002 mol/L sec = k (0.001 mol/L)2 * (0.004 mol/L)
0.002 mol/L sec = k * (0.000001 mol2 /L2) * (0.004 mol/L)
0.002 mol/L sec = k * 0.000 000 009 mol3/L3
k = 0.002 mol/L sec
0.000 000 004 mol3/L3
= 500,000 sec/mol2 L2 or sec mol-2 L-2
Therefore the rate law equation for this reaction is
rate = 500,000 sec mol-2 L-2 [NO mole/L]2 [H2 mol/L]
31. THE KEY IS TO FIND THE VALUE OF ‘k’.
r=k[A][B] (KNOWN TO BE FIRST ORDER FOR EACH REACTANT).
Therefore, k 
r
[ A][ B]
…. From trial 1: k 
0.20
5
(0.10)(0.40)
ANS:
a.
[ A] 
r
= 0.40 mol/L
k[ B]
b. you figure out equation… answer: 1.60 mol/L