CHEM 1411 Fall 2009 Practice Questions for chapters 10 and 11.
10th edition of Raymond Chang’s Chemistry.
Chapter 10:
1. Which of the following has the arrangement of electron pairs (i.e. electron-pair geometry) identical to its
molecular geometry?
(a) H2S
(b) SF4
(c) XeF4
(d) SiCl4
(e) NH3
Hint: p.p. 409-420.
2. Which of the following molecules have same molecular geometry?
(a) CO2 and CF4
(b) NH3 and BF3
(c) H2O and CS2
(d) NO3- and CO32(e) SF4 and CF4
Hint: Tables 10.1 and 10.2.
3. Which of the following is a polar molecule?
(a) CF4
(b) CO2
(c) AlCl3
(d) NH3
(e) XeF4
Hint: p.p. 420-423. Easy way to determine molecular polarity is to look at the symmetry. If a molecule
possesses symmetry, it will be non-ploar. If it does not have symmetry, then the molecule will be polar.
Usually if the central atom possesses lone pairs, it will be a polar molecule unless the lone pairs are at 180
degree angles.
4. Which of the following underlined atoms have the same hybrid orbitals?
(a) CH3COOH
(b) CH3CH=O
(c) CH3-HC=CH-CH2OH
(d) H2C=C=CH2
(e) H3C-HC=CH-CH2OH
Hint: p.p. 428-439. Hydbridization, bond angle and electron-pair geometry all are determined by total
electron pairs on the central atom.
5. How many pi bonds and sigma bonds are there in the tetracyanoethylene molecule?
N=C
C=N
C=C
N=C
C=N
(a) 9, 9
(b) 4, 5
(c) 4, 9
(d) 9, 4
(e) 5, 4
Hint: p.p. 437-439. Please add another bond between C and N to be triple bond, and add a bond between
the C of C=C and the C of C=N due to the limitation of Microsoft Word. Thanks.
6. Which of the following pairs has approximately the same bond angles?
(a) BeCl2 and BCl3
(b) CCl4 and CH3Cl
(c) AlCl4- and AlCl3
(d) PF3 and PF5
(e) CO2 and H2O
Hint: Tables 101. and 10.4.
7. What is the hybrid orbital for S in SF4?
(a) sp
(b) sp2
(c) sp3
Hint: p.p. 435-436.
(d) sp3d
8. Which of the following has the bond angle as 120 o?
(a) NH3
(b) AlCl3
(c) SF6
(d) PF3
Hint: Tables 10.1 and 10.4.
(e) sp3d2
(e) XeF4
9. Which of the following has the same bond order as H 2+?
(a) H2(b) H2
(c) He2
(d) All of the above
Hint: p. p. 441-433.
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(e) None of the above
Chapter 11
10. Which of the following order is correct concerning the boiling points?
(a) CH4 < SiH4 < GeH4 < SnH4
(b) NH3 < PH3 < AsH3 < SbH3
(c) H2S < H2Se < H2Te < H2O
(d) HF < HCl < HBr < HI
(e) CI4 < CBr4 < CCl4 < CF4
Hint: p.p. 463-468; Figure 11.6.
11. Which of the following has other intermolecular forces in addition to London dispersion force?
(a) C6H6
(b) CS2
(c) C2H4
(d) Cl2
(e) HF
Hint: p.p. 463-468.
12. Which of the following is capable of hydrogen-bonding among itself?
(a) HI
(b) KF
(c) B2H6
(d) C2H6
(e) CH3COOH
Hint: p.p.463-468
.
13. Which of the following is a correct order of boiling points?
(a) CO2 < RbF < CH3OH < CH3Br
(b) CH3Br < CO2 < CH3OH < RbF
(c) CO2 < CH3Br < CH3OH < RbF
(d) RbF < CH3OH < CO2 < CH3Br
(e) CH3OH < RbF < CH3Br < CO2
Hint: p.p. 463-468. Usually the boiling point and melting point trends are ionic compounds > network
compounds > polar compounds with hydrogen bonds > polar compounds > non-polar compounds.
14. Which of the following is responsible for the phenomenon that insect does not drown in the water?
(a) viscosity
(b) unit cell
(c) surface tension
(d) hydrogen bonding
(e) capillary effect
Hint: p. 469.
15. Pt, (195.08 amu), a face-centered cubic unit cell. What is the net number of metal atoms inside the unit
cell? What is the density (g/ cm3) of the metal if the edge of the unit cell is 3.924x10-10 m.
(a) 1, 4.8
(b) 2, 4.8
(c) 4, 4.8
(d) 2, 21.45
(e) 4, 21.45
Hint:(a) Number of atoms in the unit cell = 8x(1/8) + 6x(1/2) = 4
(b) The density of Pt metal:
First, convert molar mass to mass per atom: 195.08/6.02x10 23) = 3.239x10-22 g Pt/1 Pt atom.
Since there are 4 atoms in a unit cell, the mass per unit cell is
4x(3.239x10-22 g Pt/1 Pt atom) = 1.296x10-21g.
The volume of unit cell is (3.924x10-10 m x 1x102 cm/m)3 = 6.042x10-23 cm3
Density = mass / volume = {1.296x10-21g/(6.042x10-23 cm3 = 21.45 g/ cm3
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