AP Chem Ch 5-7 REview
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Transcript of AP Chem Ch 5-7 REview
8/3/2019 AP Chem Ch 5-7 REview
http://slidepdf.com/reader/full/ap-chem-ch-5-7-review 1/2
Nathan Ma
Period 0
AP Chemistry
Chapter 5-7 ReviewChapter 5
2. a. It represents an increase in internal energy of the system
b. The change in E is given a positive sign.c. The system is endothermic because its internal energy increases without work.
5. The work indicated by the reaction is positive, because the change in volume is negative with
constant pressure. The internal energy within the cylinder increases, so the change in internal energy isalso positive.
6. a. The container inside that larger container will give off heat to the outer container because it is a
higher heat. The sign of the q will be negative, so the process is exothermic.
b. If there is no pressure or volume change, change in internal energy is equal to change inenthalpy.
7. a. 1/2O2 + 1/2N2 → NO work will be positive
b. The heat of formation is 90.37 kJ/mol. The enthalpy is called a heat of formation becausethe compound is being formed by its constituent elements, making it a formation reaction.
9. Objects can possess kinetic energy or potential energy. Kinetic energy is the energy of motion,
while potential energy is the energy something possesses due to its position.10. The kinetic energy of a tennis ball decreases as it climbs higher.
B. the potential energy of the ball increases as it gets higher.
c. A ball twice the size would go half the distance, because its force is twice as large due to itsmass, so in the same energy, the distance it covers is only half of the other ball.
15. A lightbulb emits energy in the form of light and heat. The energy comes from the exciting of
electrons in an element, which releases the energy mostly as light and partially as heat. An adult person
radiates energy in the form of heat, which comes from the homeostatic functions of the human body.17. a. The term system refers to the area that is being studied in a reaction.
b. A closed system is where mass inside the system does not interact with mass outside the
system, and vice versa.19. a. Work is the energy needed to move an object.
b. The amount of work done is equal to the force exerted times the distance displaced.
20. a. Heat is the energy transferred from one object to another. b. Heat is transferred from one object to another when it is hotter than the other object.
24. The energy lost by system = energy gained by surrounding
b. the q of system will be negative if a system releases heat. W will be a negative number if the
system does work on the surrounding rather than the surrounding on the system.27. a. The gas has a higher temperature if the piston is fixed because the particles will have a higher
pressure, meaning higher velocities, and thus higher temperature.
b. in the first case, q remains constant and w is negative. In the second case, q is negative andw remains constant.
c. In both cases, the change in internal energy is negative.
28. a. The potential energy of the system is reduced because the distance between the two oppositecharges has increased.
b. This process makes it so that change in internal energy is lower.
c. The q and w for this process remain constant at 0.29. a. The term state function means that a property of a system is determined by the state's of the
system.
b. change in internal energy is a state function, whereas work is not a state function.
8/3/2019 AP Chem Ch 5-7 REview
http://slidepdf.com/reader/full/ap-chem-ch-5-7-review 2/2
c. Work is not a state function. It is determined from the actual course of the process, not the initial
and final states.
31. a. Enthalpy is easier to measure than change in internal energy because it does not involve the
addition of all forms of energy, but just the change in heat in a system. b. The process is exothermic, because the system is losing heat to its surroundings.
35. The chlorine gas has a higher enthalpy, because the reaction of it becoming diatomic releases
energy, meaning that the latter state has a resulting lower energy than the former state.42. The measured heat change would represent the change in enthalpy. In this case, change in enthalpy
is equal to change in internal energy because there is no pressure-volume work being done.
43. Change in H = -79kJ Change in Internal Energy= -79kj+18kj = -61 kJ45. a. The enthalpy change for the reverse would be 726.5 kJ
b. 2CH3OH + 3 O2 → 2CO2 + 4 H2O Change in H = -1453kJ
c. The forward reaction would be favored thermodynamically.
d. The magnitude of the change in enthalpy would decrease, because the system has to put inextra energy to convert the liquid water to gaseous water, meaning the total energy it release to the
surrounding is less by the amount of energy that takes.
48. Object A has a larger heat capacity because it increased the heat of the water more. b. Object A has a higher specific heat than object B.
50. Mercury would require the lowest amount of energy to raise the temperature 10K.
b. 50.0g * 10K * .14 J/gK = 7 J53. q= -100.0g * 13.8K * 4.18J/gK = -5768.4 J = 5.7684kJ / 9.55g * 39.99714g/mol = -24.2 kJ/mol
57. a. -2.500g * 15.57kJ/g = 38.925 kJ/ 2.7K = 14.417 kJ/K
b. The temperature change would have been twice as large, so 25.95 C61. P4O6 → P4 + 3O2 1640.1 kJ
P4 + 4 O2 → P4O10 -2940.1kJ
1640.1 kJ – 2940.1kJ = -1300 kJ
64. N2 + O2 → 2NO 180.7 kJNO2 → NO + ½ O2 56.55kJ
N2O → N2 + ½ O2 -81.6 kJ
180.7kJ + 56.55 kJ – 81.6 kJ = 155.65 kJ66.a. A table of standard enthalpy of formation is useful because it reduces the amount of calculations
necessary to find the enthalpy of formation.
b. The standard enthalpy of an element is 0 kJ/mol.c. 6C + 6H2 + 3O2 → C6H12O6
69. -1669.8 kJ- (-822.16kJ0 = -847.64 kJ/mol
73. 1790 kJ + (3* -285.83kJ + 3*-393.5 kJ ) = -247.99 kJ
82. 96g * 38kJ/g + 320g * 17kJ/g + 21g * 17kJ/g = 9445 kJ/lb * 1lb/16 oz * 1.5 oz= 885 kJ b. 96g * 9 Cal/g + 320g * 4 Cal/g + 21g * 4Cal/g =2228 Cal/lb * 1lb/16 oz * 1.5 oz=209 Cal