Unit 7 Kinetics and Thermodynamics Review
Review
Unit 7 Kinetics and Themochemistry
Laws of Thermodynamics
___________________: the part of the universe on which you focus your attention.
__________________________: the part of the universe that includes everything else in the universe.
_______________________ = system + surroundings
First law of thermodynamics states that the total amount of energy in the universe is constant. This defines the
___________________________________________________________.
Second law of thermodynamics states that the disorder in the universe always increases. As the disorder in the
universe increases, the energy is transformed into less usable forms. This energy is called ___________________Thus,
the efficiency of any process will always be less than 100%.
Third law of thermodynamics states that all molecular movement stops at a temperature we call _____________
______________, or 0 Kelvin (-273°C). Since temperature is a measure of molecular movement, there can be no
temperature lower than absolute zero. At this temperature, a perfect crystal has ____________________________..
Vocabulary
activation energy
enthalpy
vaporization
boiling point
catalyst
evaporation
melting point
phases
molar heat of fusion molar heat of vaporization
condensation
deposition
freezing point
entropy
solidification
spontaneous
sublimation
Gibbs free energy
Heat of reaction
1. The process of a liquid becoming a gas is called _______________________.
2. The amount of energy needed to vaporize one mole of liquid at its boiling point is called the liquids
_________________________.
3. The process of a solid becoming a gas is called _______________________.
4. Gas, Liquid, and solid are the three ______________ of matter.
5. The process of a solid becoming a liquid is called _______________________.
6. The temperature at which a liquid becomes a gas is its __________________________.
7. The amount of energy needed to melt one mole of solid at its melting point is called the solids
____________________________________.
8. The process of a gas becoming a solid is called _______________________.
9. The temperature at which a liquid becomes a solid is its _________________________.
10. The process of a gas becoming a liquid is called _______________________.
11. The process of a liquid becoming a gas at its boiling point is called _______________________.
12. The temperature at which a solid becomes a liquid is its _________________________.
13. ______________________ changes take place by themselves, without any help.
14. The ____________ __ _______________ or _____________ is used to describe how much energy is produced or
used during a chemical change.
15. The measure of randomness in a system is called ________________.
16. _____________ _______________ ______________ (∆G) stands for the value equal to the enthalpy minus the
temperature times entropy. It can be used to determine if a reaction will take place spontaneously.
17. A _____________________ is used to lower the energy required to make a reaction take place. It makes chemical
reactions go faster without being consumed.
18. ___________________ ___________________ is the amount of energy which a system has to have in order for a
chemical change to take place.
Brinkmann
2011
Unit 7 Kinetics and Thermodynamics Review
Review
Intermolecular Forces and Phase Changes
1. Intramolecular are forces of attraction within molecules.
a. _______________ bonds are between metal and non–metal ions. They involve a transfer of electrons from the
metal to the non-metal element.
b. _______________ bonds are non-metal elements sharing electrons.
Determine if each of the following bonds would be ionic, polar covalent or nonpolar covalent.
a.
H–P
c.
P–O
e.
Li – Br
b.
Mg – Cl
d.
C–H
f.
N –N
2. Intermolecular are the forces of attraction between molecules.
a. Hydrogen bonding (strongest, a very polar bond between hydrogen and either nitrogen, oxygen or fluorine. Eg.
H2O, NH3)
b. Dipole forces (second strongest, occurs with polar molecules). Eg. HCl
c.
Dispersion (weakest, occurs in nonpolar molecules, results from electrons within the molecule being re-distributed
so there is a temporary dipole). Eg. C2H4
3. What is the dominant (most important) type of intermolecular force for each of the following compounds?
a. NH3
e. H2O
b. CH4
f.
c.
g. H2S
HCl
d. F2
H2
i.
Cl2
j.
HF
h. NO2
4. Fill in the diagram (with high or low) to show
how intermolecular forces influence the
volatility, vapor pressure, and boiling
point of a substance.
5. Volatility is
weak
volatility is ____________
When IMF are…
stron
gg
volatility is __________
vapor pressure_______
vapor pressure is ______
boiling point is __________
boiling point is __________
6. Vapor pressure is
Does entropy INCREASE or DECREASE with the following phase changes. Describe molecule motion and energy.
7. As methanol (l) solidifies (s)
________________________________________________________________
8. As ice (s) turns to vapor (g)
________________________________________________________________
9. As water (g) condenses (l)
________________________________________________________________
10. As water (l) vaporizes (g)
________________________________________________________________
11. As a metal (s) melts to liquid (l)
________________________________________________________________
12. As methanol (g) turns to methanol (s)
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_________________________________________________________
2011
Unit 7 Kinetics and Thermodynamics Review
Review
Phase Diagrams
_________________ is a dynamic condition in which two opposing changes occur at equal rates in a closed system.
Change in the state of matter always involves a change in ________________________.
A phase diagram is a graph of pressure versus temperature that shows the conditions under which the phases of a
substance exist.
The ____________ _________ of a substance indicates the temperature and pressure at which all three phases coexists
at equilibrium.
The _________________ _______________ is the
temperature above which the substance cannot exist in a
liquid state.
1. The AB line is the ___________________ interface.
2. It starts at the _________________ (A), the point at
which all three states are in equilibrium.
3. It ends at the _______________ (B); above this
critical temperature and critical pressure the liquid
and vapor are indistinguishable from each other.
4. Each point along this line is the ______________ of the substance at that pressure.
5. The AD line is the interface between ______________________________.
6. The ________________ at each pressure can be found along this line.
7. Below A the substance cannot exist in the __________________.
8. Along the AC line the ______________ phases are in equilibrium; the ____________________ point at each
pressure is along this line.
9.
How would you describe the change in the substance as the
conditions change from Letter F to Letter G?
10.
How would you describe the change in the substance as the conditions
change from Letter E to Letter G?
11.
Letter C represents the _____________ ______________. The
substance cannot be in the ____________ phase above this temperature.
12. Letter B represents the _______________ ______________. This is the conditions where __________, _________,
and ________ are present.
Brinkmann
2011
Unit 7 Kinetics and Thermodynamics Review
Review
Calorimetry
Measuring heat (formerly measured in calories) is called
q = m·C·T
______________________. In the metric system, heat energy is
q = heat energy
m = mass of water
C = the specific heat capacity
T = the change in temperature
(in °C or K)
measured in in ____________________(J). The equation we use is:
1. How much heat energy is needed to raise the temperature of a 55 g sample of
aluminum from –24 °C to 94.6 °C?
2. 5.5 KJ of heat are added to an unknown 25 grams sample. The temperature of
the water is raised from 25K to 247 K. What is the unknown substance?
Substance
H2O (l)
H2O (steam)
Al (s)
Fe (s)
Specific Heat
(J/goC)
4.184
2.02
0.89
0.45
Water
Heat of fusion = 334 J/g
Heat of vaporization = 2260 J/g
3. 3.5 KJ of heat are added to a 28.2 g sample of copper at 20°C. What is the final temperature in kelvins? Specific heat
of copper is 0.0385 J/g °C
In the heating and cooling curves tutorial we learned that energy
is absorbed by a substance as it warms up, melts (fusion) or
boils (vaporization) and energy is released from a substance as
it cools down, condenses, or freezes.
Calorimetry (q=mCT) allows us to calculate the energy
changes as a substance warms or cools. (1, 3, & 5)
The energies involved in phase changes (areas 2 & 4) are the
Heat of Vaporization (liquid  gas) and the Heat of Fusion
(solid  liquid). These energies will be used as conversion
factors.
4. How much heat is necessary to change a 52.0 g sample of steam at115.0 °C into ice at -30.0 °C? This problem
requires several steps since temperature changes and a phase change takes place. Use the hints to solve.
a. Draw a graph of the change in temperature. Number each segment.
b. Steam to heat of vaporization:
c.
Heat change during phase change:
d. Heat change as water:
e. Heat change during phase change:
f.
Heat change for cooling of ice
g. Calculate the total energy change (exothermic or endothermic?).
Brinkmann
2011
Unit 7 Kinetics and Thermodynamics Review
Review
Energy Change in Chemical Reactions
1. Calculate the amount of heat produced when 34.8 g of methane, CH4, burns in excess of oxygen, according to the
following equation: CH4 + 2 O2 → CO2 + 2 H2O ΔH = ‐890.2 kJ
2. How much heat will be transferred when 5.81g of graphite reacts with excess H 2 according to the following equation?
Is the reaction endothermic or exothermic? 6C+ 3H2 → C6H6 ∆Ho = 49.03kJ
Ans: 3.95 kJ
3. How much heat will be released when 1.48g of chlorine reacts with excess phosphorous according to the following
equation? Is the reaction endothermic or exothermic? 2P + 5Cl2 → 2PCl5 ∆Ho = -866kJ
Ans: -3.62 kJ
4. How much heat will be released when 4.77g of ethanol (C2H5OH) reacts with excess O2 according to the following
equation? Is the reaction endothermic or exothermic? C2H5OH + 3O2 → 2CO2 + 3H2O ∆Ho = -791.4kJ
Ans: -81.9 kJ
5. What is the change in enthalpy when 11.8g of iron reacts with excess O 2 according to the following equation? Is the
reaction endothermic or exothermic? 3Fe + 2O2 → Fe3O4 ∆Ho = -1120.48kJ
Ans: -78.9 kJ
6. How much heat will be transferred when 14.9g of ammonia reacts with excess O 2 according to the following equation?
Is the reaction endothermic or exothermic? NH3 + 5O2 → 4NO + 6H2O ∆Ho = -1170kJ
Ans: -256 kJ
Hess’s Law
7. Calculate the standard reaction enthalpy for the photosynthesis reaction.
o
6 CO2(g) + 6 H2O(l
6H12O6(s) + 6 O2(g) Hrxn = ? kJ
8. Use the thermochemical equations shown below to determine
the enthalpy for the reaction for N2(g) + 3H2(g) → 2NH3(g)
Ans: -114.8 kJ
Chemistry 1-2
Substance
Enthalpy (∆H)
C6H12O2801.3
Ans:
kJ -1274.5 kJ/mol
6(l)
O2(g)
CO2(g)
H2O(l)
Elementary Steps
2NO2(g) + 7H2(g) → 2NH3(g) + 4H2O(l)
2NO2(g) → N2(g) + 2O2(g)
H2O(l) → H2(g) + ½ O2(g)
0 kJ/mol
-393.5 kJ/mol
-285.8 kJ/mol
Enthalpy (∆H)
∆Ho = 142.5 kJ
∆Ho = 82.5 kJ
∆Ho = -43.7 kJ
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Unit 7 Kinetics and Thermodynamics Review
Review
Energy Diagrams
Classify the following as endothermic, exothermic or neither:
_____
surroundings get hot
_____
H is negative
_____
PE diagram is uphill
_____
PE diagram is downhill
_____
energy is a product
_____
surroundings get cold
_____
H is positive
_____
products have more energy
_____
reactants have more energy
_____
energy is a reactant
Potential Energy Diagrams
Energy Diagram I
1. Is this chemical reaction endothermic or exothermic?
2. What is the activation energy for this reaction?
3. What is the heat of reactants?
4. What is the energy of the activated complex?
5. What is the heat of the products?
6. What is the heat of the reaction or enthalpy?
Energy Diagram II
Energy Diagram II
7. Is this chemical reaction endothermic or exothermic?
8. What is the activation energy for this reaction?
9. What is the heat of reactants?
10. What is the energy of the activated complex?
11. What is the heat of the products?
12. What is the heat of the reaction or enthalpy?
Energy Diagram III
Potential Energy Diagram III
13. Draw an energy diagram
Heat of reactants: 175 KJ
Heat of products:
50 KJ
Energy of activated complex: 225 KJ
Heat of reaction:
_____ KJ
Activation Energy: ______ KJ
14. Is this reaction endothermic or exothermic?
15. If a catalyst is present for this reaction, how would the energy diagram change? Show this on your diagram.
Chemistry 1-2
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Unit 7 Kinetics and Thermodynamics Review
Review
Collision Theory
C6H12O6 (s) + 6 O2(g) → 6 H2O (g) + 6 CO2 (g)
1. What happens to the concentrations of:
a. C6H12O6 & O2 as the reaction proceeds?
b. H2O + CO2 as the reaction proceeds?
2. According to the collision theory, what 3 circumstances are needed for C 6H12O6 & O2 to react?
a.
b.
c.
3. What is the activation energy for a chemical reaction?
Use the collision theory to explain the following:
Change in condition
a. Increasing the temperature
Increases/Decreases
Ex: Increases (speeds
up)
Explain why.
Ex: Molecules move faster; more molecules
collide with greater energy; activation energy
b. Increasing the concentration of C6H12O6
c. Decreasing the concentration of O2
d. Increase the surface area by chewing
up food in your mouth
e. Decreasing the temperature
f. Increasing the pressure in the container
g. Decreasing the concentration of H2O
h. Increasing the volume of the container
the reaction occurs in
i. Increasing the concentration of CO2
j. Using a catalyst (like salivary amylase)
Reaction Mechanisms
The series of steps by which a chemical reaction occurs is the ______________
_________________. Each individual chemical reaction is called an ____________
_____________. The product of an elementary reaction is an __________________.
An intermediate is a product that immediately gets used in the next reaction. The
elementary reaction with the highest _________________ ___________ has the lowest rate and is the ________
_______________ ____________.
Chemistry 1-2
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Unit 7 Kinetics and Thermodynamics Review
Review
Rate of Reaction
1. A pieces of magnesium reacts with 10 ml of 1 M hydrochloric acid. What is the rate of
the reaction? Assume the magnesium is 0.15 grams.
a. Graph the data.
Time Temperature
(Sec)
(°C)
0
21.1
10
25.6
20
30.2
30
32.4
40
33.6
50
34.6
60
35.0
b. Calculate the overall rate of the reaction.
c.
Calculate the rate of the reaction between 0 and 30 seconds.
d. Calculate the heat of the reaction based on 10 ml of water (Cp = 4.184 J/gK).
e. Is this reaction endothermic or exothermic?
2. In the gas-phase reaction I2 + Cl2 →
2] changes from 0.400 M at time = 0 to 0.300 M at time = 4 .00 min.
Calculate the average reaction rate in moles I2 consumed per liter per minute.
3. At a given temperature and for a specific time interval, the average rate of the following reaction is 1.88 x 10 -4 moles
N2 consumed per liter per second. Express the reaction rate in moles H2 consumed per liter per second and in moles
NH3 produced per liter per second.
N2 + 3H2 →
2NH3
4. Given the following data for the decomposition of hydrogen peroxide, calculate the average reaction rate in moles
H2O2 consumed per liter per minute for each time interval.
Time (min)
0
2
5
10
20
Chemistry 1-2
Concentration
H2O2 (M)
2.5
2.12
1.82
1.48
1.0
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