PSI AP Chemistry: Chemical Bonding
Name _______________________
Chapter Problems Part C Molecular Shapes and Dipole Moments
1. N2O, otherwise known as laughing gas, in used as an anesthetic.
a. What would be the correct geometry of the molecule?
b. Would the molecule be expected to have a large or small dipole
moment? Justify your answer.
c. The solubility of N2O in water is just 0.15 g/100 mL water @20C.
i. How many moles of N2O would be dissolved in 200 mL of
water?
ii. Explain what the low solubility of N2O in water tells you about
the dipole moment of the molecule.
2. Chlorate (ClO3-) and chlorite (ClO2-) have different roles. Chlorite is used to
bleach wood pulp to make white paper while chlorate are used as powerful,
although slightly unstable oxidizing agents.
a. What would be the geometries of both ions?
b. What would be the O-Cl-O bond angles in both ions?
c. Explain why the O-Cl-O bond angle is less in the chlorite ion:
d. Propose why chlorate would be a better oxidizer than would the
chlorite ion.
3. A sample taken from a factory contains carbon tetrachloride (CCl4). The
carbon tetrachloride can be extracted by mixing the sample with a solvent
the CCl4 will dissolve in.
a. What would be the Cl-C-Cl bond angle in the compound?
b. Which solvent (CH3OH or C6H14) would be better suited to extract the
CCl4? Explain your reasoning.
4. Which two factors influence the polarity of a molecule?
5. Given the following molecules:
C2H2
HCOH
CH3NH2
IF3
a.
b.
c.
d.
e.
Which of the substances contains 107 degree bond angles?
Which of the substances contain 120 degree bond angles?
Which substances would have a linear geometry?
Which substances would have a “T” shape?
Which substances would be soluble in water? Explain your reasoning
for each substance chosen:
f. Rank the substances chosen in “e” from most to least soluble in water.
Explain your reasoning.
g. IF3 can be reacted with F2 to form IF5
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i. What would be the expected geometry of IF5?
ii. Why would the bond angles be expected be smaller in IF5
compared to IF3?
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Answers
1. N2O, otherwise known as laughing gas, in used as an anesthetic.
a. What would be the correct geometry of the molecule? Linear
b. Would the molecule be expected to have a large or small dipole
moment? Justify your answer. Small, although the molecule is
asymmetrical, the EN difference is not large between O and N (only
0.5)
c. The solubility of N2O in water is just 0.15 g/100 mL water @20C.
i. How many moles of N2O would be dissolved in 200 mL of
water? 0.017 moles
ii. Explain what the low solubility of N2O in water tells you about
the dipole moment of the molecule. Must have small dipole
moment as water is polar.
2. Chlorate (ClO3-) and chlorite (ClO2-) have different roles. Chlorite is used to
bleach wood pulp to make white paper while chlorate are used as powerful,
although slightly unstable oxidizing agents.
a. What would be the geometries of both ions? Chlorate = triangular
pyramidal, chlorite = bent
b. What would be the O-Cl-O bond angles in both ions? 107, 104.5
c. Explain why the O-Cl-O bond angle is less in the chlorite ion: there are
fewer unbonded electrons in chlorate thereby allowing for greater
spacing
d. Propose why chlorate would be a better oxidizer than would the
chlorite ion. The oxidation state of Cl in chlorate is +5 compared to
in chlorite being only +3.
3. A sample taken from a factory contains carbon tetrachloride (CCl4). The
carbon tetrachloride can be extracted by mixing the sample with a solvent
the CCl4 will dissolve in.
a. What would be the Cl-C-Cl bond angle in the compound? 109.5
b. Which solvent (CH3OH or C6H14) would be better suited to extract the
CCl4? Explain your reasoning. C6H14 due to the non-polar nature of
CCl4 it will prefer a non-polar solvent as well.
4. Which two factors influence the polarity of a molecule? Polarity of bonds
and symmetry of molecule
5. Given the following molecules:
C2H2
HCOH
CH3NH2
IF3
a. Which of the substances contains 107 degree bond angles? CH3NH2
b. Which of the substances contain 120 degree bond angles? HCOH
c. Which substances would have a linear geometry? C2H2
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d. Which substances would have a “T” shape? IF3
e. Which substances would be soluble in water? Explain your reasoning
for each substance chosen: HCOH due to its larger dipole moment,
same with CH3NH2 and it’s ability to form H-bonds with H2O, and
potentially IF3 due to it’s asymmetrical shape and large EN
difference.
f. Rank the substances chosen in “e” from most to least soluble in water.
Explain your reasoning. Students “guesses” may vary here –
looking for good reasoning. A possible order may be: CH3NH2 due
to its ability to form H-bonds, HCOH due to its large dipole moment,
followed by IF3.
g. IF3 can be reacted with F2 to form IF5
i. What would be the expected geometry of IF5? Square
pyramidal
ii. Why would the bond angles be expected be smaller in IF5
compared to IF3? More bonded pairs means more repulsions,
tighter distance between atoms.
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