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

CHE 1401 - Spring 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 energy released by combustion of 1 g of a substance is called the
__________ of the substance.
A) specific heat
B) enthalpy
C) nutritional calorie content
D) heat capacity
E) fuel value
1)
2) 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) 2.66 × 104
C) 5.58 × 10-6
2)
D) 0.00558
E) 1.79 × 105
3) Of the following, which one is a state function?
A) q
B) w
C) H
D) heat
E) none of the above
3)
4) With reference to enthalpy changes, the term standard conditions means
__________.
4)
(a) P = 1 atm
(b) some common temperature, usually 298 K
(c) V = 1 L
A) a only
B) b only
C) c only
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D) a and c
E) a and b
5) 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) 48.1
B) 840
C) 2.08 × 10-2
5)
D) 54.4
E) 1.89 × 103
6) Under what condition(s) is the enthalpy change of a process equal to the
amount of heat transferred into or out of the system?
6)
(a) temperature is constant
(b) pressure is constant
(c) volume is constant
A) a only
B) b only
C) c only
D) a and b
E) b and c
7) 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) 1.00 × 103
B) 100 × 102
7)
C) 1.00
D) 50.0
E) 10.0
8) Which one of the following is an exothermic process?
A) condensation of water vapor
B) water evaporating
C) ice melting
D) boiling soup
E) Ammonium thiocyanate and barium hydroxide are mixed at 25°C: the
temperature drops.
8)
9) 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) 25.0
B) 9.0
C) 59.0
D) 34.0
E) 29.9
9)
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10) The internal energy can be increased by __________.
10)
(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
D) c only
E) b and c
11) Which one of the choices below is not considered a fossil fuel?
A) anthracite coal
B) crude oil
C) petroleum
D) natural gas
E) hydrogen
11)
12) Which of the following is a statement of the first law of thermodynamics?
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A) Ek = mν2
2
B) A negative ΔH corresponds to an exothermic process.
C) ΔE = Efinal - Einitial
D) Energy lost by the system must be gained by the surroundings.
E) 1 cal = 4.184 J (exactly)
12)
13) The units of of heat capacity are __________.
A) K/J or °C/J
B) J/K or J/°C
C) J/g-K or J/g-°C
D) J/mol
E) g-K/J or g-°C/J
13)
14) 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 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.
C) 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.
D) The ΔH of a reaction depends on the physical states of the reactants and
products.
E) The ΔH for a process in the forward direction is equal to the ΔH for the
process in the reverse direction.
14)
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15) The units of of specific heat are __________.
A) J/K or J/°C
B) g-K/J or g-°C/J
C) J/mol
D) J/g-K or J/g-°C
E) K/J or °C/J
15)
16) 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) 35.0
B) 32.3
C) 102
D) 142
E) 27.6
16)
17) For a given process at constant pressure, ΔH is negative. This means that the
process is __________.
A) equithermic
B) endothermic
C) a state function
D) exothermic
E) energy
17)
18) Which one of the following statements is true?
A) The enthalpy change of a reaction is the reciprocal of the ΔH of the reverse
reaction.
B) H is the value of q measured under conditions of constant volume.
C) The enthalphy change for a reaction is independent of the state of the
reactants and products.
D) Enthalpy is a state function.
E) Enthalpy is an intensive property.
18)
19) For which one of the following reactions is the value of ΔH°rxn equal to ΔH°f
for the product?
A) 1/2 N2 (g) + O2 (g) → NO2 (g)
B) H2 (g) + 1/2 O2 (g) → H2O (l)
C) H2 (g) + O2 (g) → H2O 2 (l)
D) 2 C (s, graphite) + 2 H2 (g) → C2H4 (g)
E) all of the above
19)
20) 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) -9.12
C) 8.20
D) -7.43
E) -12.51
20)
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21) 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) 0.0013
B) 1.7
C) 36
D) 15
E) 7.7 × 102
21)
22) For the species in the reaction below, ΔHf° is zero for __________.
22)
2Co (s) + H2 (g) + 8PF3 (g) → 2HCo(PF3)4 (l)
A) PF3 (g)
B) Co (s)
C) HCo(PF3)4 (l)
D) H2 (g)
E) both Co(s) and H2 (g)
23) The combustion of titanium with oxygen produces titanium dioxide:
23)
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) -311
B) 4.98
C) -1.49 × 104
D) -0.154
E) 2.67
24) 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) 2Ca (s) + O2 (g) → 2CaO (s)
C) 3Mg (s) + N2 (g) → Mg3N2 (s)
D) C2H2 (g) + H2 (g) → C2H4 (g)
E) 2C (graphite) + O2 (g) → 2CO (g)
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24)
25) Of the substances below, the highest fuel value is obtained from __________.
A) charcoal
B) hydrogen
C) wood
D) bituminous coal
E) natural gas
25)
26) The internal energy of a system is always increased by __________.
A) adding heat to the system
B) adding heat to the system and having the system do work on the
surroundings
C) a volume compression
D) withdrawing heat from the system
E) having the system do work on the surroundings
26)
27) 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
27)
28) For which one of the following equations is ΔH°rxn equal to ΔHf° for the
product?
A) 2CO (g) + O2 (g) → 2CO2 (g)
B) CH4 (g) + 2Cl2 (g) → CH2Cl2 (l) + 2HCl (g)
C) Xe (g) + 2F2 (g) → XeF4 (g)
D) C (diamond) + O2 (g) → CO2 (g)
E) N2 (g) + O3 (g) → N2O 3 (g)
28)
29) 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) 22.9
B) 0.0113
C) 88.6
D) 1221
E) 429
29)
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30) For which one of the following reactions is the value of ΔH°rxn equal to ΔH°f
for the product?
A) N2 (g) + O2 (g) → 2 NO (g)
B) 2 H2 (g) + O2 (g) → 2 H2O (g)
C) 2 C (s, graphite) + 2 H2 (g) → C2H4 (g)
D) H2O (l) + 1/2 O2 (g) → H2O2 (l)
E) 2 H2 (g) + O2 (g) → 2 H2O (l)
30)
31) A __________ ΔH corresponds to an __________ process.
A) negative, endothermic
B) negative, exothermic
C) positive, exothermic
D) zero, exothermic
E) zero, endothermic
31)
32) Objects can possess energy as __________.
32)
(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
33) For which one of the following reactions is ΔH°rxn equal to the heat of
formation of the product?
A) 6C (s) + 6H (g) → C6H6 (l)
B) (1/2)N2 (g) + O2 (g) → NO 2 (g)
C) 12C (g) + 11H2 (g) + 11O (g) → C6H22O11 (g)
D) N2 (g) + 3H2 (g) → 2NH3 (g)
E) P (g) + 4H (g) + Br (g) → PH4Br (l)
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33)
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) -11.5
B) -23.1
C) -0.0217
D) 1.44
E) -2.31 × 104
35) The reaction
4Al (s) + 3O2 (g) → 2Al2O3 (s)
35)
ΔH° = -3351 kJ
is __________, and therefore heat is __________ by the reaction.
A) exothermic, released
B) exothermic, absorbed
C) endothermic, absorbed
D) endothermic, released
E) thermoneutral, neither released nor absorbed
36) 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.
36)
37) 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) 60.29
B) 5.120 × 10-3
C) 1054
D) 3415
E) Additional information is needed to complete the calculation.
37)
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38) Which one of the following conditions would always result in an increase in the
internal energy of a system?
A) The system gains heat and does work on the surroundings.
B) The system gains heat and has work done on it by the surroundings.
C) The system loses heat and does work on the surroundings.
D) The system loses heat and has work done on it by the surroundings.
E) None of the above is correct.
38)
39) In the reaction below, ΔHf° is zero for __________.
39)
Ni (s) + 2CO (g) + 2PF3 (g) → Ni(CO) 2(PF3)2 (l)
A) PF3 (g)
B) CO (g)
C) Ni (s)
D) Ni(CO) 2(PF3)2 (l)
E) both CO (g) and PF3 (g)
40) The most abundant fossil fuel is __________.
A) hydrogen
B) petroleum
C) uranium
D) coal
E) natural gas
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40)