12) A gas absorbs 0.0 J of heat and then performs 13.1 J of work. The change in internal energy of the gas
is
A) 26.2 J
B) 13.1 J
C) -26.2 J
D) -13.1 J
13) When 2.00 mol of benzene is vaporized at a constant pressure of 1.00 atm and at its normal boiling
point of 80.1°C, 67.8 kJ are absorbed and PΔV for the vaporization process is equal to 5.80 kJ then
A) ΔE = 62.0 kJ and ΔH = 67.8 kJ.
B) ΔE = 73.6 kJ and ΔH = 67.8 kJ.
C) ΔE = 67.8 kJ and ΔH = 73.6 kJ.
D) ΔE = 67.8 kJ and ΔH = 62.0 kJ.
14) When 6.000 moles of H2(g) reacts with 3.000 mol of O2(g) to form 6.000 mol of H2O(l) at 25°C and a
constant pressure of 1.00 atm. If 409.8 kJ of heat are released during this reaction, and PΔV is equal to –
22.20 kJ, then
A) ΔH° = +409.8 kJ and ΔE° = +432.0 kJ.
B) ΔH° = +409.8 kJ and ΔE° = +387.6 kJ.
C) ΔH° = –409.8 kJ and ΔE° = -387.6 kJ.
D) ΔH° = –409.8 kJ and ΔE° = –432.0 kJ.
15) At a constant pressure of 2.50 atm what is the enthalpy change ΔH for a reaction where the internal
energy change ΔE is 58.0 kJ and the volume increase is 12.6 L? (1 L·atm = 101.325 J.)
A) 39.1 kJ
B) 54.8 kJ
C) 61.2 kJ
D) 76.9 kJ
16) At 1 atm pressure, the heat of sublimation of gallium is 277 kJ/mol and the heat of vaporization is 271
kJ/mol. To the correct number of significant figures, how much heat is required to melt 1.50 mol of
gallium at 1 atm pressure?
A) 6 kJ
B) 9 kJ
C) 268 kJ
D) 271 kJ
17) How much heat is absorbed/released when 20.00 g of NH3(g) reacts in the presence of excess (g) to
produce NO(g) and H2O(l) according to the following chemical equation?
4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(l) ΔH° = 1168 kJ
A) 342.9 kJ of heat are absorbed.
B) 342.9 kJ of heat are released.
C) 1372 kJ of heat are absorbed.
D) 1372 kJ of heat are released.
18) How much heat is absorbed when 30.00 g of C(s) reacts in the presence of excess SO2(g) to produce
CS2(l) and CO(g) according to the following chemical equation?
5 C(s) + 2 SO2(g) → CS2(l) + 4 CO(g) ΔH° = 239.9 kJ
A) 119.8 kJ
B) 239.9 kJ
C) 599.2 kJ
D) 1439 kJ
19) At constant pressure, the combustion of 25.0 g of C2H6(g) releases 1300 kJ of heat. What is ΔH for the
reaction given below?
2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(l)
A) -215 kJ
B) -390 kJ
C) -1560 kJ
D) -3120 kJ
20) The heat of vaporization of water at 100°C is 40.66 kJ/mol. Calculate the quantity of heat that is
absorbed/released when 7.00 g of steam condenses to liquid water at 100°C.
A) 15.8 kJ of heat are absorbed.
B) 15.8 kJ of heat are released.
C) 105 kJ of heat are absorbed.
D) 105 kJ of heat are released.
21) When 0.500 mol of CH4(g) reacts with excess Cl2(g) at constant pressure according to the chemical
equation shown below, 354 kJ of heat are released. Calculate the value of ΔH for this reaction, as written.
2 CH4(g) + 3 Cl2(g) → 2 CHCl3(l) + 3 H2(g) ΔH = ?
A) -1416 kJ
B) -708.0 kJ
C) +708.0 kJ
D) +1416 kJ
22) Calculate the total quantity of heat required to convert 25.0 g of liquid CCl4(l) from 45.0°C to gaseous
CCl4 76.8°C (the normal boiling point for CCl4)? The specific heat of CCl4(l) is its heat of
fusion is and its heat of vaporization is
A) 0.681 kJ
B) 1.21 kJ
C) 5.53 kJ
D) 6.06 kJ
23) How much heat is transferred per 5.00 moles of NH3(g) formed in the reaction shown below?
N2(g) + 3 H2(g) → 2 NH3(g) ΔH° = – 92.2 kJ
A) 92.2 kJ
B) 230 kJ
C) 461 kJ
D) 154 kJ
24) The specific heat of copper is 0.385 J/(g ∙ °C). If 34.2 g of copper, initially at 21.0°C, absorbs 4.689 kJ,
what will be the final temperature of the copper?
A) 21.4°C
B) 23.8°C
C) 356°C
D) 377°C
25) It takes 11.2 kJ of energy to raise the temperature of 145 g of benzene from 22.0°C to 67.0°C. What is
the specific heat of benzene?
A) 1.15 J/(g ∙ °C)
B) 1.72 J/(g ∙ °C)
C) 3.48 J/(g ∙ °C)
D) 5.18 J/(g ∙ °C)
26) When 5.50 g of Ba(s) is added to 100.00 g of water in a container open to the atmosphere, the reaction
shown below occurs and the temperature of the resulting solution rises from 22.00°C to 61.16°C. If the
specific heat of the solution is 4.18 J/(g ∙ °C), calculate for the reaction, as written.
Ba(s) + 2 H2O(l) → Ba(OH)2(aq) + H2(g) = ?
A) -431 kJ
B) -3.14 kJ
C) +3.14 kJ
D) +431 kJ
27) Sodium metal reacts with water to produce hydrogen gas and sodium hydroxide according to the
chemical equation shown below. When 0.015 mol of Na is added to 100.00 g of water, the temperature of
the resulting solution rises from 25.00°C to 31.45°C. If the specific heat of the solution is 4.18 J/(g ∙ °C),
calculate ΔH for the reaction, as written.
2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g) ΔH = ?
A) -5.41 kJ
B) -90.0 kJ
C) -180 kJ
D) -360 kJ
28) When 50.0 mL of 0.400 M Ca(NO3)2 is added to 50.0 mL of 0.800 M NaF, CaF2 precipitates, as shown
in the net ionic equation below. The initial temperature of both solutions is 25.00°C. Assuming that the
reaction goes to completion, and that the resulting solution has a mass of 100.00 g and a specific heat of
4.18 J/(g ∙ °C), calculate the final temperature of the solution.
Ca2+(aq) + 2 F–(aq) → CaF2(s) ΔH° = -11.5 kJ
A) 24.45°C
B) 25.55°C
C) 26.10°C
D) 26.65°C
29) When 1.820 g of anthracene, C14H10, is combusted in a bomb calorimeter that has a water jacket
containing 500.0 g of water, the temperature of the water increases by 34.52°C. Assuming that the specific
heat of water is 4.18 J/(g ∙ °C), and that the heat absorption by the calorimeter is negligible, estimate the
enthalpy of combustion per mole of anthracene.
A) +39.7 kJ/mol
B) -39.7 kJ/mol
C) -7070 kJ/mol
D) -8120 kJ/mol
30) Which is expected to have the lowest specific heat capacity at 25°C?
A) air
B) gold
C) ethylene glycol
D) methanol
44
31) 10.0 g of a metal, initially at 25°C, are placed into 10.0 g of water, initially at 100°C. Which metal will
have the highest final temperature? Shown after each metal is its specific heat in J/(g∙°C).
A) sodium (1.23)
B) calcium (0.650)
C) lead (0.160)
D) nickel (0.440)
32) Given: 4 NO2(g) + O2(g) → 2 N2O5(g) ΔH° = -110.2 kJ
find ΔH° for 8 N2O5(g) → 16 NO2(g) + 4 O2(g).
A) -220.4 kJ
B) -440.8 kJ
C) 440.8 kJ
D) 220.4 kJ
33) Find ΔH for BaCO3 (s) → BaO (s)+ CO2 (g)
given 2 Ba (s) + O2 (g) → 2 BaO (s) ΔH = -1107.0 kJ
Ba (s) + CO2 (g) + 1/2 O2 (g) → BaCO3 (s) ΔH = -822.5 kJ
A) -1929.5 kJ
B) +1376 kJ
C) -269.0 kJ
D) 269.0 kJ
34) Find ΔH for C3H8 (g) + 6 H2O (g) → 3 CO2 (g) + 10 H2
given C3H8 (g) + 3 H2O (g) → 3 CO (g) + 7 H2 (g) ΔH = 499 kJ
CO (g) + H2O (g) → CO2 (g) + H2 (g) ΔH = -41 kJ
A) 376 kJ
B) 458 kJ
C) 540 kJ
D) -622 kJ
35) For which should the standard heat of formation ΔH°f, be zero at 25°C?
A) O(g)
B) O2(g)
C) NaI(s)
D) CBr4
36) Which is expected to have the most negative standard enthalpy of formation?
A) N2(g)
B) C5H12(g)
C) HBr(g)
D) H2O(g)
37) Acetylene torches utilize the following reaction:
2 C2H2(g) + 5 O2(g) → 4 CO2(g) + 2 H2O(g)
Use the given standard enthalpies of formation to calculate ΔH° for this reaction.
A) 1603kJ
B) -1256.2 kJ
C) 2512.4 kJ
D) -2512.4 kJ
38) For which reaction is H expected to be most positive?
A) Cl2(g) → 2 Cl(g)
B) I2(g) → 2 I(g)
C) 2 Cl(g) → Cl2(g)
D) 2 I(g) → I2(g)
39) Which is expected to have the largest carbon-oxygen bond dissociation energy?
A) CO
B) CO2
C) H2CO3
D) HCOOH
40) At a given temperature and pressure, which of the following would be expected to have the greatest
molar entropy?
A) F2 (s)
B) F2 (l)
C) F2 (g)
D) All of these would be expected to have the same molar entropy.
41) At a given temperature and pressure, which of the following would be expected to have the greatest
molar entropy?
A) I2(s)
B) I2(l)
C) I2(g)
D) All of these would be expected to have the same molar entropy.
42) For the reaction, N H3(g) → N(g) + 3 H(g), one would expect
A) ΔH° to be negative and ΔS° to be negative.
B) ΔH° to be negative and ΔS° to be positive.
C) ΔH° to be positive and ΔS° to be negative.
D) ΔH° to be positive and ΔS° to be positive.
43) For the freezing of liquid hexane, C6H, at a given temperature and pressure,
A) ΔH is negative and ΔS is negative.
B) ΔH is negative and ΔS is positive.
C) ΔH is positive and ΔS is negative.
D) ΔH is positive and ΔS is positive.
44) Which is not a spontaneous process?
A) combustion of gasoline to produce carbon dioxide and water
B) diffusion of perfume in a room
C) dissolution of powdered punch in water
D) freezing of water at 3°C
45) He gas is contained in a one-liter flask that is connected to an empty one-liter flask with a closed
stopcock between the two flasks. When the stopcock is opened some of the He enters the evacuated flask.
For this system
A) ΔH is negative and ΔS is zero.
B) ΔH is zero and ΔS is positive.
C) ΔH is zero and ΔS is negative.
D) ΔH is positive and ΔS is positive.
46) For the conversion of ice to water at 0°C and 1 atm,
A) ΔG is zero, ΔH is positive, and ΔS is negative.
B) ΔG is zero, ΔH is positive, and ΔS is positive.
C) ΔG is negative, ΔH is positive, and ΔS is negative.
D) ΔG is positive, ΔH is zero, and ΔS is positive.
47) Calculate Gibb’s free energy and determine if the event is spontaneous or non-spontaneous for ΔH =
42 Jand ΔS = -111 J/K at 400 K.
A) 86.4 kJ, spontaneous
B) 86.4 kJ, non-spontaneous
C) -2.4 kJ, spontaneous
D) -2.4 kJ, non-spontaneous
9.3 Short Answer Questions
1) The law of conservation of energy is also known as the ________ law of thermodynamics.
2) Energy can be classified as either ________ energy (energy of motion) or ________ energy (stored
energy).
3) Kinetic energy increases with increasing ________ and increasing ________.
4) The SI unit for energy is the ________.
5) ________ energy is the kinetic energy of molecular motion.
6) Is thermal energy a form of kinetic or potential molecular energy?
7) Is a hydroelectric dam a form of kinetic or potential molecular energy?
8) The sum of the potential and kinetic energies for every molecule or ion in a system is the ________
energy of the system and is given the symbol ________.
9) A property whose value depends only on the present condition of the system and not how the system
arrived at that condition is called a ________ function.
10) In the reaction below, is energy released or absorbed by the system? What is the sign of the energy
change, E?
432 kJ + A + 2B → 3C
11) When the reaction below is performed in a water bath, will the temperature of the water bath increase
or decrease?
432 kJ + A + 2 B → 3 C
12) A reaction for which ΔE = -850 kJ is one in which products have 850 kJ ________ internal energy than
the reactants, and products are ________ stable than the reactants.
13) Heat transferred in a chemical reaction or physical change is expressed as ΔE when the heat is
transferred under constant ________ and is expressed as ΔH when heat is transferred under constant
________ conditions.
14) In the reaction shown below, ________ kJ of heat are released per mole of carbon dioxide(g) that is
produced.
C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g) ΔH = -2045 kJ
15) Because the number of moles of gas are increasing from 6 to 7 in the reaction shown below, at
constant pressure ΔE is predicted to be slightly ________ negative than ΔH.
C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g)
16) A reaction is performed in a 1-L balloon at 25°C and 1 atm pressure. At the end of the reaction the
balloon has expanded to 1.5 L and the surface of the balloon has a temperature of 35°C and is at 1 atm
pressure. Determine whether the signs of the heat transferred, the work, and the energy change,
respectively, are positive or negative.
17) A reaction that absorbs 49.6 kJ from the surroundings in a vessel that undergoes a volume decrease of
1.25 L at a constant 4.00 atm pressure has an energy change, ΔE = ________ kJ.
18) When 1.0 mole of MgSO4 is dissolved in water contained in a calorimeter, the temperature of the
water and dissolved ions increases. Therefore the sign of ΔH for this reaction is ________, heat is
transferred ________ the system ________ the surroundings, and the reaction is classified as ________.
19) A reaction is performed in a water bath initially at 28°C which decreases to 10°C by the end of the
reaction. For this reaction the sign of heat transfer is ________, and the reaction is classified as ________.
20) Heat transfer measured in a coffee-cup calorimeter at constant pressure is a measure of ________, but
heat transfer measured in a bomb calorimeter at constant volume is a measure of ________.
21) For the reaction: A + 2 B → 3 C, ΔH° = -203 kJ. For the reaction 12 C → 4 A + 8 B, ΔH° = ________ kJ.
22) The sign of ΔS° for reaction below is expected to be ________.
2 H2(g) + O2(g) → 2 H2O(g)
23) A spontaneous reaction has a ________ value of ΔG and is favored by a ________ value of ΔH and a
________ value of ΔS.
24) The sign of ΔG for a reaction is ________ if the reaction is spontaneous, ________ if the reaction is at
equilibrium, and ________ if the reaction is nonspontaneous.
25) At 253 K the sign of ΔG for the physical change shown below is ________.
H2O(s) → H2O(l)