Download State University of New York College at Oneonta Chem 111, Exam 2

State University of New York College at Oneonta
Chem 111, Exam 2
Thursday, November 4, 2010
1.
Given the thermochemical equation
2Al(s) + 32 O2(g) → Al2O3(s)
∆H = –1676 kJ
find ∆H for the following reaction.
2Al2O3(s) → 4Al(s) + 3O2(g)
a) –1676 kJ
2.
c) 838 kJ
d) 1676 kJ
e) 3352 kJ
What is the change in enthalpy at 25°C and 1 atm for the reaction of 7.00 mol of iron (II)
oxide with excess oxygen gas?
6FeO(s) + O2(g) → 2Fe3O4(s); ∆H° = –610 kJ
a)
3.
b) –838 kJ
–610 kJ
b) –712 kJ
c) –87.1 kJ
d) 14.5 kJ
e) 610 kJ
Consider the following thermochemical equation:
N2(g) + 2O2(g) → 2NO2(g); ∆H° = 66.2 kJ
From this equation, we may conclude that 66.2 kJ is the quantity of heat that is
a)
b)
c)
d)
e)
4.
lost to the surroundings when 1 mol of O2 is consumed at constant pressure.
lost to the surroundings when 1 mol of NO2 is formed at constant pressure.
gained from the surroundings when 2 mol of NO2 is formed at constant pressure.
gained from the surroundings when 1 mol of NO2 is formed at constant pressure.
lost from the surroundings when 2 mol of NO2 is formed at constant pressure.
How much heat is evolved upon the complete oxidation of 9.41 g of aluminum at 25°C and
1 atm pressure? (∆H of for Al2O3 is –1676 kJ/mol.)
4Al(s) + 3O2(g) → 2Al2O3(s)
a) 146 kJ
5.
b) 1169 kJ
c) 292 kJ
d) 585 kJ
e) 1.58 × 104 kJ
A 170.0-g sample of metal at 78.0°C is added to 170.0 g of H2O(l) at 15.0°C in an insulated
container. The temperature rises to 17.9°C. Neglecting the heat capacity of the container,
what is the specific heat of the metal? The specific heat of H2O(l) is 4.18 J/(g · °C).
a) 20.8 J/(g · °C)
b) 0.201 J/(g · °C)
c) –0.201 J/(g · °C)
e) 4.18 J/(g · °C)
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d) 86.9 J/(g · °C)
6.
Given:
Pb(s) + PbO2(s) + 2H2SO4(l) → 2PbSO4(s) + 2H2O(l); ∆H° = –509.2 kJ
SO3(g) + H2O(l) → H2SO4(l); ∆H° = –130. kJ
determine ∆H° for the following thermochemical equation.
Pb(s) + PbO2(s) + 2SO3(g) → 2PbSO4(s)
a)
7.
–3.77 × 103 kJ
b) 3.77 × 103 kJ c) –639 kJ
d) –521 kJ
e) –769 kJ
What is the standard enthalpy change for the combustion of gaseous propylene, C3H6?
C3H6(g) + 92 O2(g) → 3CO2(g) + 3H2O(l)
Substance
∆H°f (kJ/mol)
C3H6(g)
+20.4
CO2(g)
–393.5
H2O(l)
–285.8
a)
–2058.3 kJ
b) –2017.5 kJ
c) –658.9 kJ
d) +2017.5 kJ e)
+2058.3 kJ
8.
Which of the following compounds is soluble in water?
a) PbCl2
b) Pb(NO3)2
c) PbI2
d) PbBr2
e) PbSO4
9.
The net ionic equation for the reaction of calcium bromide and sodium phosphate contains
which of the following species?
a) Ca2+(aq)
b) PO43–(aq)
c) 2Ca3(PO4)2(s)
d) 6NaBr(aq)
e) 3Ca2+(aq)
10. What is the net ionic equation for the neutralization of sulfuric acid with potassium
hydroxide?
a) H+(aq) + OH–(aq) → H2O(l)
b) 2H+(aq) + 2KOH(aq) → 2H2O(l) + 2K+(aq)
c) H2SO4(aq) + 2KOH(aq) → 2H2O(l) + K2SO4(aq)
d) H2SO4(aq) + 2OH–(aq) → 2H2O(l) + SO42–(aq)
e) H2S(aq) + 2KOH(aq) → 2H2O(l) + K2S(aq)
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11. In which one of the following is the oxidation number of nitrogen given incorrectly?
a) H2N2O2 (+1)
b) N2H4 (–2)
c) NaN3 (–1)
d) HNO2 (+3)
e) N2O3 (+3)
12. All of the following reactions can be described as displacement reactions except
a) Fe(s) + 2HCl(aq) → FeCl2(g) + H2(g).
b) CH4(g) + Br2(g) → CH3Br(g) + HBr(g).
c) Mg(s) + Hg(NO3)2(aq) → Mg(NO3)2(aq) + Hg(l).
d) 3CuCl2(aq) + 2Al(s) → 3Cu(s) + 2AlCl3(aq).
e) CuSO4(aq) + Ni(s) → NiSO4(aq) + Cu(s).
13. What is the molarity of hydrochloric acid in a solution containing 65.4 g of HCl in 265 mL
of solution?
a) 247 M
b) 0.00405 M c) 0.247 M
d) 6.77 M
e) 4.05 M
14. What mass of oxalic acid dihydrate, H2C2O4 · 2H2O, is required to prepare 280.0 mL of a
1.51 M solution of oxalic acid?
a) 136 g
b) 53.3 g
c) 190 g
d) 38.1 g
e) 126 g
15. An impure sample of benzoic acid (C6H5COOH, 122.12 g/mol) is titrated with 0.1278 M
NaOH. A 0.503798-g sample requires 23.81 mL of titrant to reach the endpoint. What is
the percent by mass of benzoic acid in the sample?
C6H5COOH(aq) + NaOH(aq) → NaC6H5COO(aq) + H2O(l)
a) 0.002492%
b)
100.0%
c) 0.3043%
d) 73.76%
e)
2.492%
16. What is the wavelength of a photon having a frequency of 87.9 THz? (1 THz = 1015 Hz, c =
3.00 × 108 m/s, h = 6.63 × 10-34 J • s)
a) 3.41 × 1015 nm
b) 5.83 × 10–23 nm
c) 1.75 × 10–14 nm
d) 3.41 nm
e) 0.293 nm
17. The relationship among the speed, wavelength, and frequency of electromagnetic radiation
in vacuum is
c


a)  
b)  
c) c    
d) c 
e)   c

c

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18. Which type of electromagnetic radiation has the lowest frequency?
a) ultraviolet
b) infrared
c) microwaves
d) radio waves
e) visible
19. What is the wavelength of photons that have molar energy of 541 kJ/mol? (c = 3.00 × 108
m/s, h = 6.63 × 10-34 J • s, NA = 6.02 × 1023 mol-1)
a) 3.68 × 10–22 nm
b) 8.99 × 10–10 nm
c) 221 nm
d) 1.36 × 106 nm
e) 2.21 × 105 nm
20. What is the energy per mole of photons with a wavelength of 482.6 nm? (c = 3.00 × 108
m/s, h = 6.63 × 10-34 J • s, NA = 6.02 × 1023 mol-1)
a) 2.91 × 1014 kJ/mol
b) 4.12 × 10–19 kJ/mol
c) 3.74 × 1035 kJ/mol
d) 2.48 × 102 kJ/mol
e) 6.22 × 1014 kJ/mol
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NAME______________________________________________
SECTION NUMBER______
CHEM 111 EXAM 2
Odago
Circle your answers within the space provided for Part I of the exam, and for Part II answer any
two questions showing your work clearly. Partial credit may be given if logical steps are shown
clearly.
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Part II Attempt any two questions is this section. Show your workings steps very clearly.
21.
An industrial process for manufacturing sulfuric acid, H2SO4(aq), uses hydrogen sulfide,
H2S(g), from the purification of natural gas. In the first step of this process, the hydrogen
sulfide is burned to obtain sulfur dioxide, SO2(g), according to the following unbalanced
equation.
H2S(g) + O2(g)  H2O(l) + SO2(g)
(i)
Balance the above chemical equation. (2 pts)
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(iii)
For the correctly balanced equation, ΔHo = -1125 kJ. The density of sulfur
dioxide at 25 oC and 1.00 atm is 2.62 g/L. How much heat would be evolved in
producing 23.5 mL of SO2(g) at these conditions? (4 pts)
(iii) The concentration of Pb2+ in a sample of wastewater is to be determined by using
gravimetric analysis. To a 100.0-mL sample of the wastewater is added an excess of
sodium sulfide, forming the insoluble lead (II) sulfide (239.266 g/mol) according to the
balanced equation given below. The solid lead (II) sulfide is dried, and its mass is
measured to be 0.1209 g. What was the concentration of Pb2+ in the original wastewater
sample?
Pb2+(aq) + Na2S(aq) → PbS(s) + 2Na+(aq)
(4pts)
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22. What is the standard enthalpy of formation of liquid butyraldehyde, CH3CH2CH2CHO(l)?
CH3CH2CH2CHO(l) + 52 O2(g) → 4H2O(l) + 4CO2(g); ∆H° = –2471.8 kJ
Given that
Substance
∆H°f (kJ/mol)
CO2(g)
–393.5
H2O(l)
–285.8
7
23. How many moles of photons are required to heat 600 mL of water from 25 oC to 74
o
C using a microwave oven that emits radiation with a wavelength of 123 nm?
(Given that, h =6.626 x 10-34 Js, c = 2.998 x 108 m/s, specific heat capacity of water = 4.184
J/(g. oC), density of water = 1g/mL)
(10pts)
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