Chapter 11
Critical Thinking Exercise
Solutions and Their Colligative Properties
Iodized salt contains the compound KI to supplement dietary iodine. Use the information below
to calculate the lattice energy for KI with the Born-Haber cycle.
Hsub for K(s) = 89.0 kJ/mol
Ionization energy K(g) = 418.8 kJ/mol
Hfo for KI(s) = -327.9 kJ/mol
Hsub for I2(s) = 62.4 kJ/mol
Bond energy I2(g) = 151 kJ/mol
Electron affinity I(g) = -295.2 kJ/mol
1. What is the chemical reaction equation for the formation of one mole of KI(s) from it
elements?
a. K(s) + I2(s)  KI2(s)
b. K(s) + I2(g)  KI2(s)
c. K(s) + ½ I2(s)  KI(s)
d. K(s) + ½ I2(g)  KI(s)
e. K(g) + ½ I2(s)  KI(g)
2. What is the energy needed for the sublimation of iodine?
a. -44.5 kJ
b. 44.5 kJ
c. 62.4 kJ
d. 31.2 kJ
e. -31.2 kJ
3. What is the energy needed for the sublimation of potassium?
a. -89.0 kJ
b. 89.0 kJ
c. 62.4 kJ
d. 31.2 kJ
e. -31.2 kJ
4. What is the energy needed to form I(g)?
a. 151 kJ
b. -151 kJ
c. ½(151) kJ
e. 302 kJ
5. What is the lattice energy for KI?
a. + 647.2 kJ/mol b. -647.2 kJ/mol
d. -½(151) kJ
c. 647 kJ/mol
d. -647 kJ/mol e. 679 kJ/mol
6. When 0.640 g of epinephrine is dissolved in 36.0 g of benzene, the freezing point depression
is 0.500 C. What is the molar mass for epinephrine? (Kf for benzene is 5.07 °Ckg/mol)
a. 153
b. 169
c. 180.
d. 207
e. 220.
7. The structure of epinephrine is given in Question 9. Is the experimental molar mass the same,
less than, or greater than the molar mass for the actual chemical formula for epinephrine?
a. the same
b. less than
d. greater than
8. Are hydrogen bonds present in the solid?
a. yes
b. no
9. Which area(s) of the structure is(are ) nonpolar?
a. a
b. b
c. b and d
d. a and e
a
OH
a
c
HO
e
H
N
HO
a
e. b, c, d
d
b
10. Epinephrine is dissolved in water for use in EpiPens. What area(s) of the structure is(are) make
it water-soluble?
a. a
b. b
c. b and d
d. a and e
e. b, c, d