CHEM 101 WINTER 08-09 EXAM III
On the answer sheet (Scantron) write you name, student ID number, and recitation section number. Choose the
best (most correct) answer for each question and enter it on your answer sheet.
Avogadro’s Number: 6.022 × 1023 mol-1
Speed of Light: c = 3.00 x 108 mys-1
Planck’s Constant: h = 6.626 x 10-34 Jys
Rydberg Constant: R = 2.179 x 10-18 J
E = hc/λ = hυ
q = m c ΔT
1 cal = 4.184 J
1. Please choose the letter “a” as your answer for this question.
2. The temperature of 3.50 kg of water is raised by 1.17°C when 1.00 g of hydrazine N2H4 is burned in a bomb
calorimeter. The calorimeter has a heat capacity of 883 J/°C. How much heat is given off by the sample?
a. 0.944 kJ
b. 16.3 kJ
c. 17.1 kJ
d. 18.2 kJ
e. 21.5 kJ
3. Based on the following thermochemical equation below, which statement is false?
N2(g) + 3 H2(g)
2 NH3(g)
H° = − 46.11 kJ
a.
b.
c.
d.
e.
For the reverse process, H° = + 46.11 kJ.
The value of 46.11 kJ applies to the formation of two moles of NH3.
The value of 92.22 kJ applies to the reaction of two moles of N2 and three moles of H2.
Per mole of N2, H° = −46.11 kJ.
Per mole of H2, H° = −15.37 kJ.
4. Determine the heat of reaction for the process
TiO2(s) + 4HCl(g)
TiCl4(l) + 2H2(g) + O2(g)
using the information given below:
Ti(s) + O2(g)
TiO2(s)
2HCl(g)
H2(g) + Cl2(g)
Ti(s) + 2Cl2(g)
a.
b.
c.
d.
e.
−320.1 kJ
−233.7 kJ
233.7 kJ
320.1 kJ
504.7 kJ
TiCl4(l)
H° = −939.7 kJ
H° = −184.6 kJ
H° = −804.2 kJ
5. The standard enthalpies of formation for several substances are given below:
CO(g)
CO2(g)
−393.5 kJ/mol
−110.5 kJ/mol
H2O(l)
H2O(g)
−241.8 kJ/mol
−285.8 kJ/mol
H2O2(l)
CH3OH(g)
−200.7 kJ/mol
−187.8 kJ/mol
C2H5OH(l)
C
H
OH(g)
−235.1 kJ/mol
−277.7 kJ/mol
2 5
Determine the heat of vaporization for H2O and C2H5OH.
a. 241.8 and −235.1 kJ
b. 241.8 and 325.1 kJ
c. 44.0 and 42.6 kJ
d. −54.0 and −42.6 kJ
e. −44.0 and −42.6 kJ
6. The standard enthalpies of formation for several substances are given below:
FeS2(s) = −178.2 kJ/mol
FeCl2(s) = −341.8 kJ/mol
FeCl3(s) = −399.5 kJ/mol
HCl(g) = −92.3 kJ/mol
HCl(aq) = −167.1 kJ/mol
H2S(g) = −20.6 kJ/mol
H2O(g) = −271.8 kJ/mol
Calculate the H° for the reaction below.
2FeCl2(s) + 2HCl(g)
2FeCl3(s) + H2(g)
a. −219.0 kJ
b. −69.2 kJ
c. 34.6 kJ
d. 69.2 kJ
e. 219.0 kJ
7. Which traits make for the best fuel?
a. low fuel value and high energy density
b. high fuel value and low energy density
c. weak bonds in the fuel and weak bonds in the combustion products
d. weak bonds in the fuel and strong bonds in the combustion products
e. strong bonds in the fuel and strong bonds in the combustion products
8. Which statement concerning the interaction between two atoms is incorrect?
a. If two atoms are widely separated, there is very little attraction between them.
b. When two atoms are one bond length apart, the electrons on one atom are attracted to the
nucleus of the other atom.
c. When two atoms have very little separation between them, repulsion occurs.
d. A covalent bond occurs when electrons are shared between two nuclei.
e. As atoms get closer together, their electrons attract each other.
9. Which statement about covalent bonds is false?
a. Covalent bonds allow atoms to achieve a filled outermost electron shell.
b. Covalent bonds are unreactive.
c. Covalent bonds occur in molecular compounds.
d. Covalent bonds involve valence electrons.
e. Covalent bonds form between non-metal atoms.
10. Which element will have four electrons in its Lewis symbol?
a. aluminum
b. beryllium
c. carbon
d. magnesium
e. oxygen
11. How many electrons will be in the correctly drawn Lewis Structure for CCl4?
a. 32
b. 74
c. 35
d. 8
e. 11
12. Which of the following statements could not describe a covalent bond?
a. The sharing of two electrons between two atoms
b. The sharing of four electrons between two atoms
c. An electrostatic interaction between two oppositely charged ions
d. The sharing of two or more electrons equally between two atoms
e. The sharing of two or more electrons unequally between two atoms
13. Determine the number of electrons that the four elements below require to achieve an octet of electrons.
nitrogen oxygen carbon fluorine
a.
1
3
2
4
b.
3
4
2
2
c.
3
2
4
1
d.
4
3
5
2
e.
5
6
4
7
14. Which statement about hydrocarbons is false?
a. Hydrocarbons can be straight-chain alkanes or branch-chain alkanes.
b. Methane is the simplest hydrocarbon.
c. Saturated hydrocarbons contain only C−H and C−C single covalent bonds.
d. Hydrocarbons contain hydrogen, carbon, and other non-metals, such as oxygen.
e. Hydrocarbons can contain carbon atoms joined in a ring.
15. Which molecule does not contain a multiple bond?
a. H2O2
b. C2H2
c. CH2O
d. CO2
e. O2
16. Write the correct Lewis dot structure for CCl2O. Which statement correctly describes the structure?
a. The structure contains 3 single bonds, 1 double bond, and 2 lone pairs.
b. The structure contains 3 single bonds, 1 triple bond, and 8 lone pairs.
c. The structure contains 2 single bonds, 1 double bond, and 2 lone pairs.
d. The structure contains 2 single bonds, 1 double bond and 8 lone pairs.
e. The structure contains 1 single bond, 1 triple bond, and 2 lone pairs.
17. Assume all hydrocarbons given are linear. Which compound will contain a double bond?
a. C3H6
b. C6H10
c. C2H2
d. CH4
e. C5H12
18. Which of the following compounds can exhibit cis-trans isomerism?
a. CH2=CH2
b. CH3CH3
c. H2C=O
d. ClHC=CHCl
e. Cl2C=CH2
19. Which bond is shortest?
a. carbon−oxygen single bond
b. carbon−hydrogen single bond
c. hydrogen−hydrogen single bond
d. carbon−carbon double bond
e. carbon−oxygen triple bond
20. Which bond is strongest?
a. carbon−nitrogen triple bond
b. carbon−nitrogen double bond
c. carbon−hydrogen bond
d. carbon−oxygen triple bond
e. carbon−carbon single bond
21. Which bond is least polar?
a. C−C
b. C−N
c. N−H
d. C−F
e. C−O
22. Which element is the most electronegative?
a. sulfur
b. iodine
c. nitrogen
d. aluminum
e. carbon
23. What is the formal charge on carbon in HCN?
a. −2
b. −1
c. 0
d. +1
e. +2
24. Which of the following species does not have resonance structures?
a. CO
b. SO2
c. H2O
d. NO
e. O3
25. Write the singly bonded Lewis dot structure for BF3. Which of the following statements best describes this
structure?
a. It obeys the octet rule on all atoms.
b. It has less than an octet on at least one atom.
c. It has a lone pair of electrons on the boron atom.
d. It has less than an octet of electrons on all atoms.
e. It exceeds the octet rule.
26. A list of non-metals is given below. Which entire set of elements cannot exceed the octet rule?
B Si N P O S F Cl
a. Si, P, S, Cl
b. B, N, O, F
c. O, S, F, Cl
d. B, Si, N, P
e. All eight elements can exceed the octet rule.