Unit 9: Molecular Shape
REVIEW
Paper 1 Questions:
1. In which of the following are compounds BF3, CH4, CO2 and SF6 arranged in decreasing order of
bond angle? [May 2001 24]
A. BF3, CH4, CO2 SF6
B. BF3, SF6, CO2 CH4
C. CO2, BF3, CH4, SF6
D. SF6, CO2, CH4, BF3
2. The following compounds have similar molar masses. Which compound has the highest boiling
point? [May 2002 35]
A. CH3COOH
B. C2H5OCH3
C. CH3COCH3
D. C2H5Cl
3. Which of the following is true for CO2? [May 2003 11]
A.
B.
C.
D
C=O bond
Polar
Non-polar
Polar
Non-polar
CO2 molecule
Non-polar
Polar
Polar
Non-polar
4. The molar masses of C2H6, CH3OH and CH3F are very similar. How do their boiling points compare?
[ May 2003 12]
A. C2H6<CH3OH<CH3F
B. CH3F<CH3OH<C2H6
C. CH3OH<CH3F< C2H6
D. C2H6< CH3F <CH3OH
5. Which substance is most soluble in water (in mol dm-3) at 298K? [May 2004 11]
A. CH3CH3
B. CH3OCH3
C. CH3CH2OH
D. CH3CH2CH2CH2OH
6. What is the molecular shape and hybridization of the nitrogen atom in NH3? [May 2004 12]
A.
B.
C.
D.
Molecular Shape
tetrahedral
trigonal planar
trigonal pyramidal
trigonal pyramidal
Hybridization
sp3
sp2
sp2
sp3
7. Which statement about sigma and pi bonds is correct? [May 2004 13]
A. Sigma bonds are formed only by s orbitals and pi bonds are formed only by p orbitals.
B. Sigma bonds are formed only by p orbitals and pi bonds are formed only by s orbitals.
C. Sigma bonds are formed by either s or p orbitals, pi bonds are formed only by p orbitals.
D. Sigma and pi bonds are formed by either s or p orbitals.
IB Chemistry HL-­‐Yr 1: Unit 9 Review 2/3 8. In ethanol, C2H5OH (l), there are covalent bonds, hydrogen bonds and van der Waals’ forces. Which
bonds or forces are broken when ethanol is vaporized? [ May 2005 10]
A. Only hydrogen bonds
B. Covalent bonds and hydrogen bonds
C. Covalent bonds and van der Waals’ forces
D. Hydrogen bonds and van der Waals’ forces
9. Which statement is correct about multiple bonding between carbon atoms? [May 2005 12]
A. Double bonds are formed by two π bonds.
B. Double bonds are weaker than single bonds.
C. π bonds are formed by overlap between s orbitals.
D. π bonds are weaker than sigma bonds.
10. In which substance is hydrogen bonding present? [May 2006 12]
A. CH4
B. CH2F2
C. CH3CHO
D. CH3OH
11. Which is the most volatile substance? [May 2006 13]
A. Chlorine
B. Fluorine
C. Sodium chloride
D. Sodium fluoride
12. Which is the smallest bond angle in the PF5 molecule? [May 2006 14]
A. 90°
B. 109.5°
C. 120°
D. 180°
13. Which types of hybridization are shown by the carbon atoms in the compound
CH2 = CH – CH3? [May 2006 15]
I. sp
II. sp2
III. sp3
A.
B.
C.
D.
I and II only
I and III only
II and III only
I, II and III
IB Chemistry HL-­‐Yr 1: Unit 9 Review 3/3 Paper 2 Questions
1. [May 2004 8c]
(i)
List the following substances in order of increasing boiling points (lowest first).
CH3CHO
C2 H6
CH3COOH
C2H5OH
[2]
(ii)
State whether each compound is polar or non-polar, and explain the order of boiling points in
(i)
[8]
2. The letters W, X, Y and Z represent four consecutive elements in the periodic table. The number of
electrons in the highest occupied energy levels are:
[May 2005 7]
W: 3, X:4, Y:5, Z:6
(a) Write the formula for;
(i) An ionic compound formed from W and Y, showing the charges
(ii) A covalent compound containing X and Z
(b)
[2]
Outline the principles of the valence shell electron pair repulsion (VSEPR) theory. [3]
(c) For the following compounds
PCl3, PCl5, POCl3
(i)
Draw a Lewis structure for each molecule in the gas phase. (Show all non-bonding electron
pairs).
[3]
(ii) State the shape of each molecule and predict the bond angles.
[6]
(iii) Deduce whether or not each molecule is polar, giving a reason for your answer. [3]
(d) (i) Explain the meaning of the term hybridization.
[1]
(ii) Discuss the bonding in the molecule CH3CHCH2 with reference to
-­‐ The formation of σ and π bonds
-­‐ The length and strength of the carbon-carbon bonds
-­‐ The types of hybridization shown by the carbon atoms
[6]