Download CHE 1401 - Fall 2015 - Chapter 5 Homework 5 (Chapter 5

CHE 1401 - Fall 2015 - Chapter 5
Homework 5 (Chapter 5: Thermochemistry)
_______________________________________________________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the
question.
1) The British thermal unit (Btu) is commonly used in engineering applications. A
Btu is defined as the amount of heat required to raise the temperature of 1 lb of
water by 1°F. There are __________ joules in one Btu. 1 lb = 453.59 g; °C =
(5/9)(°F - 32°); specific heat of H2O (l) = 4.18 J/g-K.
A) 3415
B) 1054
C) 60.29
D) 5.120 × 10-3
E) Additional information is needed to complete the calculation.
1)
2) Which one of the following conditions would always result in an increase in the
internal energy of a system?
A) The system loses heat and has work done on it by the surroundings.
B) The system gains heat and has work done on it by the surroundings.
C) The system gains heat and does work on the surroundings.
D) The system loses heat and does work on the surroundings.
E) None of the above is correct.
2)
3) A 50.0-g sample of liquid water at 25.0 C is mixed with 29.0 g of water at
45.0°C. The final temperature of the water is ________°C. The specific heat
capacity of liquid water is 4.18 J/g-K.
A) 102
B) 27.6
C) 142
D) 35.0
E) 32.3
3)
4) The specific heat capacity of methane gas is 2.20 J/g-K. How many joules of
heat are needed to raise the temperature of 5.00 g of methane from 36.0°C to
75.0°C?
A) 0.0113
B) 88.6
C) 1221
D) 429
E) 22.9
4)
5) Which of the following is a statement of the first law of thermodynamics?
A) 1 cal = 4.184 J (exactly)
B) ΔE = Efinal - Einitial
C) Ek = 1 mν2
2
D) A negative ΔH corresponds to an exothermic process.
E) Energy lost by the system must be gained by the surroundings.
5)
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6) For which one of the following reactions is the value of ΔH°rxn equal to ΔH°f
for the product?
A) H2 (g) + O2 (g) → H2O 2 (l)
B) 1/2 N2 (g) + O2 (g) → NO2 (g)
C) H2 (g) + 1/2 O2 (g) → H2O (l)
D) 2 C (s, graphite) + 2 H2 (g) → C2H4 (g)
6)
E) all of the above
7) Which one of the following statements is true?
A) Enthalpy is an intensive property.
B) H is the value of q measured under conditions of constant volume.
C) The enthalpy change of a reaction is the reciprocal of the ΔH of the reverse
reaction.
D) Enthalpy is a state function.
E) The enthalphy change for a reaction is independent of the state of the
reactants and products.
7)
8) The combustion of titanium with oxygen produces titanium dioxide:
8)
Ti (s) + O2 (g) → TiO2 (s)
When 0.721 g of titanium is combusted in a bomb calorimeter, the temperature
of the calorimeter increases from 25.00°C to 53.80°C. In a separate experiment,
the heat capacity of the calorimeter is measured to be 9.84 kJ/K. The heat of
reaction for the combustion of a mole of Ti in this calorimeter is __________
kJ/mol.
A) 2.67
B) -1.49 × 104
C) 4.98
D) -0.154
E) -311
9) Under what condition(s) is the enthalpy change of a process equal to the
amount of heat transferred into or out of the system?
(a) temperature is constant
(b) pressure is constant
(c) volume is constant
A) a only
B) b only
C) c only
2
D) a and b
E) b and c
9)
10) With reference to enthalpy changes, the term standard conditions means
__________.
10)
(a) P = 1 atm
(b) some common temperature, usually 298 K
(c) V = 1 L
A) a only
B) b only
C) c only
D) a and b
E) a and c
11) The internal energy of a system is always increased by __________.
A) having the system do work on the surroundings
B) a volume compression
C) adding heat to the system and having the system do work on the
surroundings
D) withdrawing heat from the system
E) adding heat to the system
11)
12) Which one of the following is an exothermic process?
A) boiling soup
B) water evaporating
C) ice melting
D) condensation of water vapor
E) Ammonium thiocyanate and barium hydroxide are mixed at 25°C: the
temperature drops.
12)
13) When a system __________, ΔE is always negative.
A) absorbs heat and has work done on it
B) gives off heat and has work done on it
C) gives off heat and does work
D) absorbs heat and does work
E) none of the above is always negative.
13)
14) The units of of specific heat are __________.
A) J/K or J/°C
B) K/J or °C/J
C) g-K/J or g-°C/J
D) J/mol
E) J/g-K or J/g-°C
14)
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15) The specific heat capacity of liquid water is 4.18 J/g-K. How many joules of heat
are needed to raise the temperature of 5.00 g of water from 25.1°C to 65.3°C?
A) 2.08 × 10-2
15)
B) 48.1
C) 54.4
D) 840
E) 1.89 × 103
16) The energy released by combustion of 1 g of a substance is called the
__________ of the substance.
A) nutritional calorie content
B) enthalpy
C) heat capacity
D) fuel value
E) specific heat
16)
17) For a given process at constant pressure, ΔH is negative. This means that the
process is __________.
A) energy
B) endothermic
C) a state function
D) equithermic
E) exothermic
17)
18) At what velocity (m/s) must a 20.0 g object be moving in order to possess a
kinetic energy of 1.00 J?
A) 50.0
B) 1.00
C) 1.00 × 103
D) 10.0
E) 100 × 102
18)
19) For which one of the following equations is ΔH°rxn equal to ΔHf° for the
product?
A) 2CO (g) + O2 (g) → 2CO2 (g)
B) C (diamond) + O2 (g) → CO2 (g)
C) N2 (g) + O3 (g) → N2O 3 (g)
D) Xe (g) + 2F2 (g) → XeF4 (g)
E) CH4 (g) + 2Cl2 (g) → CH2Cl2 (l) + 2HCl (g)
19)
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20) In the reaction below, ΔHf° is zero for __________.
20)
Ni (s) + 2CO (g) + 2PF3 (g) → Ni(CO) 2(PF3)2 (l)
A) CO (g)
B) Ni(CO) 2(PF3)2 (l)
C) PF3 (g)
D) Ni (s)
E) both CO (g) and PF3 (g)
21) For which one of the following reactions is the value of ΔH°rxn equal to ΔHf°
for the product?
A) C (diamond) + O2 (g) → CO2 (g)
B) C2H2 (g) + H2 (g) → C2H4 (g)
C) 3Mg (s) + N2 (g) → Mg3N2 (s)
21)
D) 2C (graphite) + O2 (g) → 2CO (g)
E) 2Ca (s) + O2 (g) → 2CaO (s)
22) For the species in the reaction below, ΔHf° is zero for __________.
22)
2Co (s) + H2 (g) + 8PF3 (g) → 2HCo(PF3)4 (l)
A) HCo(PF3)4 (l)
B) Co (s)
C) H2 (g)
D) PF3 (g)
E) both Co(s) and H2 (g)
23) What is the enthalpy change (in kJ) of a chemical reaction that raises the
temperature of 250.0 ml of solution having a density of 1.25 g/ml by 7.80 oC?
(The specific heat of the solution is 3.74 joules/gram-K.)
A) 6.51
B) -7.43
C) 8.20
D) -9.12
E) -12.51
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23)
24) Which of the following is a statement of Hess's law?
A) If a reaction is carried out in a series of steps, the ΔH for the reaction will
equal the sum of the enthalpy changes for the individual steps.
B) The ΔH of a reaction depends on the physical states of the reactants and
products.
C) The ΔH for a process in the forward direction is equal to the ΔH for the
process in the reverse direction.
D) If a reaction is carried out in a series of steps, the ΔH for the reaction will
equal the product of the enthalpy changes for the individual steps.
E) The ΔH for a process in the forward direction is equal in magnitude and
opposite in sign to the ΔH for the process in the reverse direction.
24)
25) Of the substances below, the highest fuel value is obtained from __________.
A) natural gas
B) hydrogen
C) bituminous coal
D) wood
E) charcoal
25)
26) Of the following, which one is a state function?
A) heat
B) H
C) q
D) w
E) none of the above
26)
27) A 6.50-g sample of copper metal at 25.0°C is heated by the addition of 84.0 J of
energy. The final temperature of the copper is ________°C. The specific heat
capacity of liquid water is 0.38 J/g-K.
A) 59.0
B) 25.0
C) 29.9
D) 9.0
E) 34.0
27)
28) The units of of heat capacity are __________.
A) J/K or J/°C
B) J/g-K or J/g-°C
C) g-K/J or g-°C/J
D) J/mol
E) K/J or °C/J
28)
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29) The specific heat capacity of liquid mercury is 0.14 J/g-K. How many joules of
heat are needed to raise the temperature of 5.00 g of mercury from 15.0°C to
36.5°C?
A) 36
B) 15
C) 7.7 × 102
D) 0.0013
E) 1.7
29)
30) For which one of the following reactions is ΔH°rxn equal to the heat of
formation of the product?
A) 12C (g) + 11H2 (g) + 11O (g) → C6H22O11 (g)
B) (1/2)N2 (g) + O2 (g) → NO 2 (g)
C) 6C (s) + 6H (g) → C6H6 (l)
D) P (g) + 4H (g) + Br (g) → PH4Br (l)
E) N2 (g) + 3H2 (g) → 2NH3 (g)
30)
31) The specific heat capacity of solid copper metal is 0.385 J/g-K. How many
joules of heat are needed to raise the temperature of a 1.55-kg block of copper
from 33.0°C to 77.5°C?
A) 26.6
B) 0.00558
C) 1.79 × 105
31)
D) 5.58 × 10-6
E) 2.66 × 104
32) Which one of the choices below is not considered a fossil fuel?
A) petroleum
B) natural gas
C) crude oil
D) hydrogen
E) anthracite coal
32)
33) The most abundant fossil fuel is __________.
A) coal
B) petroleum
C) natural gas
D) hydrogen
E) uranium
33)
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34) Hydrogen peroxide decomposes to water and oxygen at constant pressure by
the following reaction:
2H2O2 (l) → 2H2O (l) + O 2 (g)
34)
△H = -196 kJ
Calculate the value of q (kJ) in this exothermic reaction when 4.00 g of hydrogen
peroxide decomposes at constant pressure?
A) -23.1
B) -11.5
C) 1.44
D) -0.0217
E) -2.31 × 104
35) Objects can possess energy as __________.
35)
(a) endothermic energy
(b) potential energy
(c) kinetic energy
A) a only
B) b only
C) c only
D) b and c
E) a and c
36) A __________ ΔH corresponds to an __________ process.
A) negative, endothermic
B) negative, exothermic
C) positive, exothermic
D) zero, exothermic
E) zero, endothermic
36)
37) The reaction
37)
4Al (s) + 3O2 (g) → 2Al2O3 (s)
ΔH° = -3351 kJ
is __________, and therefore heat is __________ by the reaction.
A) exothermic, released
B) endothermic, released
C) endothermic, absorbed
D) exothermic, absorbed
E) thermoneutral, neither released nor absorbed
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38) For which one of the following reactions is the value of ΔH°rxn equal to ΔH°f
for the product?
A) 2 H2 (g) + O2 (g) → 2 H2O (g)
B) H2O (l) + 1/2 O2 (g) → H2O2 (l)
C) 2 C (s, graphite) + 2 H2 (g) → C2H4 (g)
D) 2 H2 (g) + O2 (g) → 2 H2O (l)
E) N2 (g) + O2 (g) → 2 NO (g)
38)
39) A chemical reaction that absorbs heat from the surroundings is said to be
__________ and has a __________ ΔH at constant pressure.
A) endothermic, positive
B) endothermic, negative
C) exothermic, negative
D) exothermic, positive
E) exothermic, neutral
39)
40) The internal energy can be increased by __________.
40)
(a) transferring heat from the surroundings to the system
(b) transferring heat from the system to the surroundings
(c) doing work on the system
A) a only
B) a and c
C) b only
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D) c only
E) b and c