PRACTICE EXERCISE

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PRACTICE EXERCISE Of Br2, Ne, HCl, HBr, and N2,
which is likely to have (a) the largest
intermolecular dispersion forces, (b) the largest
dipole-dipole attractive forces?
Answers (a) Br2 (largest molecular weight), (b)
HCl (largest polarity)
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PRACTICE EXERCISE In which of the following
substances is significant hydrogen bonding
possible methylene chloride (CH2Cl2) phosphine
(PH3) hydrogen peroxide (HOOH), or acetone
(CH3COCH3)?
Answer HOOH
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PRACTICE EXERCISE (a) Identify the intermolecular
forces present in the following substances, and
(b) select the substance with the highest boiling
point CH3CH3, CH3OH, and CH3CH2OH.
Answers (a) CH3CH3 has only dispersion forces,
whereas the other two substances have both
dispersion forces and hydrogen bonds (b) CH3CH2OH
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PRACTICE EXERCISE What is the enthalpy change
during the process in which 100.0 g of water at
50.0C is cooled to ice at 30.0C? (Use the
specific heats and enthalpies for phase changes
given in Sample Exercise 11.4.)
Answer 20.9 kJ 33.4 kJ 6.27 kJ 60.6 kJ
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PRACTICE EXERCISE At what external pressure will
ethanol have a boiling point of 60C?
Answer about 340 torr (0.45 atm)
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PRACTICE EXERCISE Using Figure 11.27(b), describe
what happens when the following changes are made
in a CO2 sample initially at 1 atm and 60ºC
(a) Pressure increases at constant temperature to
60 atm. (b) Temperature increases from 60ºC to
20ºC at constant 60 atm pressure.
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PRACTICE EXERCISE The element iron crystallizes
in a form called ?-iron which has a body-centered
cubic unit cell. How many iron atoms are in the
unit cell?
Answer two
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PRACTICE EXERCISE The body-centered cubic unit
cell of a particular crystalline form of iron is
2.8664 Å on each side. Calculate the density of
this form of iron.
.Answer 7.8753 g/cm3
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Fig 11.19
Figure 11.19 Heating curve for water. This graph
indicates the changes that occur when 1.00 mol of
water is heated from 25C to 125C at a constant
pressure of 1 atm. Blue lines show the heating of
one phase from a lower temperature to a higher
one. Red lines show the conversion of one phase
to another at constant temperature.
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Fig 11.24
Figure 11.24 Vapor pressure for four common
liquids as a function of temperature. The
temperature at which the vapor pressure is 760
torr is the normal boiling point of each liquid.
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Fig 11.27b
Figure 11.27 Phase diagrams of H2O and CO2. The
axes are not drawn to scale in either case. In
(b), for carbon dioxide, note the triple point X
(56.4C, 5.11 atm), the normal sublimation point
Y (78.5C, 1 atm), and the critical point Z
(31.1C, 73.0 atm).
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Table 11.5
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Table 11.7
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