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11: Intermolecular Forces and Liquids

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    204590
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    General Questions

    Exercise \(\PageIndex{1}\)

    What is the dominant intermolecular force in H2?

    1. London Dispersion (instantaneous dipole-induced dipole)
    2. dipole-dipole
    3. ion-dipole
    4. hydrogen bonding
    Answer

    a. London Dispersion (instantaneous dipole-induced dipole)

    Exercise \(\PageIndex{2}\)

    What is the major intermolecular force in H2O? 

    1. London Dispersion (induced dipole-induced dipole)
    2. dipole-dipole
    3. ion-dipole
    4. hydrogen bonding
    Answer

    d. hydrogen bonding

    Exercise \(\PageIndex{3}\)

    What is the major intermolecular force responsible for the dissolution of NaCl in H2O?

    1. London Dispersion (induced dipole-induced dipole)
    2. dipole-dipole
    3. ion-dipole
    4. hydrogen bonding
    Answer

    c. ion-dipole

    Exercise \(\PageIndex{4}\)

    Which force is strongest?

    1. dipole/dipole
    2. ion/dipole
    3. London Dispersion
    4. covalent
    Answer

    d. covalent

    Exercise \(\PageIndex{5}\)

    Hydrogen bonding is a special case of:

    1. dipole-dipole forces
    2. ion-dipole forces
    3. covalent bonding
    4. London Dispersion Forces
    Answer

    a. dipole-dipole force

    Exercise \(\PageIndex{6}\)

    Which has the highest boiling point? (F2, Cl2, Br2, I2)

    Answer

    d. I2, these are all homonuclear diatomics, and Iodine is both the heaviest (largest mass) and most polarizable (largest volume).

    Exercise \(\PageIndex{7}\)

    Which has the highest boiling point? (HF, HCl, HI, HBr)

    Answer

    a. HF, although it is the lightest (which would have you think it would have a low boiling point), it has strong hydrogen bonds, which take a lot of energy to overcome, and so has a high boiling point.

    Exercise \(\PageIndex{8}\)

    Which of the following molecules are not involved with hydrogen bonding?

    1. H2,NH3
    2. HI,HBr
    3. HF,NH3
    4. HCOOH,H2O
    Answer

    b. HI, HBr

    Exercise \(\PageIndex{9}\)

    Which has the lowest boiling point? (He, Ne, Kr, Ar)

    Answer

    a. He

    Exercise \(\PageIndex{10}\)

    Which is more polarizable? (O, S, Se, Te)

    Answer

    d. Te

    Exercise \(\PageIndex{11}\)

    Placed the following compounds in the order of instantaneous dipole, dipole/dipole and hydrogen bonding as the primary intermolecular forces. (H2O, H2Se, CH4)

    Answer

    CH4, H2Se, H2O

    Exercise \(\PageIndex{12}\)

    Arrange the following compounds in order of increasing boiling points. (H2O, H2S, H2Se, H2Te)

    Answer

    H2S < H2Se < H2Te < H2O

    Exercise \(\PageIndex{13}\)

    Arrange the following compounds in order of increasing boiling point. (H2O, HF, NH3, CH4)

    Answer

    CH4 < NH3 < HF < H2O

    Exercise \(\PageIndex{14}\)

    Which compound is the most polarizable? (I2, H2, F2, Br2)

    Answer

    I2

    Exercise \(\PageIndex{15}\)

    Which species cannot be involved with hydrogen bonding? (HF, H2O, NH3, NH4+)

    Answer

    NH4+

    Exercise \(\PageIndex{16}\)

    What intermolecular force is responsible for the dissolution of oxygen into water?

    1. hydrogen bonding
    2. instantaneous-induced dipole
    3. dipole-induced dipole
    4. dipole-dipole
    Answer

    C. dipole-induced dipole

    Exercise \(\PageIndex{17}\)

    Which has the highest boiling point? (CH4, SiH4, GeH4, SnH4)

    Answer

    SnH4

    Exercise \(\PageIndex{18}\)

    Which has the lowest boiling point? (CH4, SiH4, GeH4, SnH4)

    Answer

    CH4

    Exercise \(\PageIndex{19}\)

    Which has the highest boiling point? (NH3, PH3, CH4, SiH4)

    Answer

    NH3

    Exercise \(\PageIndex{20}\)

    What angle best approximates the geometric structure of ice? (90°, 109°, 120°, 180°)

    Answer

    109°

    clipboard_ebe114bc5bf00942a5c531ad8f3280286.png
    11.1: Vapor pressure of four different compounds.  Use figure 11.1 to solve the following questions.

    Exercise \(\PageIndex{21}\)

    Which set of curves would represent the effect of increasing temperature on the vapor pressure of a liquid?

    1. A & B
    2. C & D
    3. All of them
    4. None of them
    Answer

    a. A & B

    Exercise \(\PageIndex{22}\)

    The normal boiling point is defined as: 

    1. 100°C

    2. The boiling pt. at 1 atm

    3. The boiling pt. on planet earth

    4. None of the above

    Answer

    b. The boiling pt. at 1 atm

    Exercise \(\PageIndex{23}\)

    The normal boiling point of diethyl ether is 34.6°C and of water is 100°C. Which has the higher vapor pressure at 20°C?

    1. water
    2. diethyl ether
    3. they are the same
    4. it depends on your elevation
    Answer

    b. diethyl ether

    Exercise \(\PageIndex{24}\)

    If one of the compounds in question 1 is diethyl ether and the other is water, curve___is diethyl ether and curve___is water.

    1. A,B
    2. B,A
    3. C,D
    4. D,C
    Answer

    a. A,B

    Exercise \(\PageIndex{25}\)

    A liquid is _____  and assumes _____ of its container whereas a gas is _____ and assumes _____ of its container.

    1. Compressible, the volume and shape, condensed, the shape
    2. Compressible, the volume, compressible, the volume and shape
    3. Condensed, the volume and shape, condensed, the volume and shape
    4. Not compressible, the shape of a portion, compressible, the volume and shape
    5. Not compressible, the volume and shape, compressible, the shape
    Answer

    d. Not compressible, the shape of a portion, compressible, the volume and shape

    Exercise \(\PageIndex{26}\)

    Choose the following molecule that exhibits dipole-dipole attractions? (AsH3, BCl3, Cl2, CO2, XeF4)

    Answer

    AsH3

    Exercise \(\PageIndex{27}\)

    What is the predominant intermolecular force in KBr?

    1. Dipole-dipole attraction
    2. Hydrogen-bonding
    3. Ion-dipole attraction
    4. Ionic bonding
    5. London-dispersion forces
    Answer

    d. Ionic bonding

    Exercise \(\PageIndex{28}\)

    What are the principal difference in the normal boiling points of ICl (97°C; molecular mass 162 amu) and Br2 (59°C; molecular mass 160 amu)?

    1. Both dipole-dipole interactions and London-dispersion forces
    2. Both hydrogen-bonding and dipole-dipole interactions
    3. Dipole-dipole interactions
    4. Hydrogen bonding
    5. London-dispersion forces
    Answer

    c. Dipole-dipole interactions

    Exercise \(\PageIndex{29}\)

    Explain the reason why iodine is a solid, bromine is a liquid, and chlorine is a gas at room temperature.

    Answer

    Van der Waals forces increase going down the periodic table. Thus Chlorine has the weakest van der Waals forces and Iodine has the strongest with bromine being in the middle.

    Exercise \(\PageIndex{30}\)

    The _____ is the attractive force between an instantaneous dipole and an induced dipole.

    1. Dipole-dipole attraction
    2. Hydrogen-bonding
    3. Ion-dipole attraction
    4. Ionic bonding
    5. London dispersion forces
    Answer

    e. London dispersion forces

    Exercise \(\PageIndex{31}\)

    Choose the ethane molecule that has the highest boiling point.

    1. C2Br6
    2. C2Cl6
    3. C2F6
    4. C2H6
    5. C2I6
    Answer

    e. C2I6

    Exercise \(\PageIndex{1=32}\)

    What is the major attractive force that exists among different I2 (elemental iodine, I2, is a solid at room temperature) molecules in the solid?

    1. Covalent-ionic interactions
    2. Dipole-dipole attractions
    3. Dipole-dipole rejections
    4. Ionic-dipole interactions
    5. London dispersion forces
    Answer

    e. London dispersion forces

    Exercise \(\PageIndex{33}\)

    Hydrogen bonding is a special case of what other intermolecular forces?

    1. Dipole-dipole attractions
    2. Ion-dipole attraction
    3. Ion-ion interactions
    4. London-dispersion forces
    5. None of these
    Answer

    a. Dipole-dipole attractions

    Exercise \(\PageIndex{34}\)

    Which of the following has the highest boiling point? (N2, Br2, H2, Cl2, O2)

    Answer

    Br2

    Exercise \(\PageIndex{35}\)

    The molecules in C12H26 are held together by _____.

    1. Dipole-dipole interactions
    2. Dispersion forces
    3. Hydrogen bonding
    4. Ion-dipole interactions
    5. Ion-ion interactions
    Answer

    b. Dispersion forces

    Exercise \(\PageIndex{36}\)

    The shape of a liquid’s meniscus is determined by _____.

    1. the relative magnitudes of cohesive forces in the liquid and adhesive forces between the liquid and its container
    2. the type of material the container is made of
    3. the viscosity of the liquid
    4. the volume of the liquid
    Answer

    a. the relative magnitudes of cohesive forces in the liquid and adhesive forces between the liquid and its container

    Exercise \(\PageIndex{37}\)

    Viscosity is _____.

    1. Inversely proportional to molar mass
    2. The “skin” on a liquid surface caused by intermolecular attraction
    3. The resistance to flow
    4. The same as density
    5. Unaffected by temperature
    Answer

    c. The resistance to flow

    Exercise \(\PageIndex{38}\)

    What property is responsible for the “beading up” of water?

    1. density
    2. hydrogen bonding
    3. surface tension
    4. vapor pressure
    5. viscosity
    Answer

    c. surface tension

    Exercise \(\PageIndex{39}\)

    Explain which substance in each of the following pairs is likely to have the higher normal melting point: (a) HCl or NaCl; (b) C2H5OC2H5 (diethyl ether) or C4H9OH (butanol); (c) CHI3 or CHF3; (d) C2H4 or CH3OH

    Answer a

    NaCl, because it is an ionic compound not molecular

    Answer b

    butanol due to hydrogen bonding in butanol not in diethyl ether

    Answer c

    CHI3 because of stronger London dispersion forces

    Answer d

    CH3OH due to hydrogen bonding

    Exercise \(\PageIndex{40}\)

    Explain which substance in each of the following pairs is likely to have the higher normal melting point: (a) H2S or H2O; (b) NH3 or PH3; (c) KBr or CH3Br; (d) CH4 or SiH4.

    Answer a

    H2O because hydrogen bonding is stronger than dipole-dipole bonds

    Answer b

    NH3 because hydrogen bonding can occur with 2 of the molecules

    Answer c

    KBr due to being an ionic compound not molecular

    Answer d

    SiHdue to stronger intermolecular forces and electrons

    Exercise \(\PageIndex{41}\)

    Predict the shapes of each of the following molecules and identify the member of each pair with the higher boiling point using VESPR models: (a) PBr3 or PF3; (b) SO2 or CO2; (c) BF3 or BCl3.

    Answer a

    PBr3 due to stronger dipole-dipole bonds

    Answer b

     SOdue to dipole-dipole bonds being stronger than London dispersion forces

    Answer c

    BClhas stronger van der Waal's forces

    Exercise \(\PageIndex{42}\)

    Determine which liquid in each of the following pairs has the greater surface tension: (a) cis-dichloroethene or trans-dichloroethene; (b) benzene at 20°C or benzene at 60°C.

    Answer a

    cis-dichloroethene due to the molecule being polar and having both dipole-dipole and van der Waals forces

    Answer b

    benzene at 20°C due to stronger intermolecular forces at a cooler temperature

    Exercise \(\PageIndex{43}\)

    Rank the following molecules in order of increasing viscosity at 50°C: C6H5SH, C6H5OH, C6H6.

    Answer

    C6H6 < C6H5SH < C6H5OH

    Exercise \(\PageIndex{44}\)

    The boiling point of chloroform (CHCl3) is lower than that of carbon tetrachloride (CCl4). Since chloroform is polar and carbon tetrachloride is not, with consideration of the dipole-dipole forces would predict that chloroform would have the higher boiling point. How can we account for the observed order of the boiling points?

    Answer

    Carbon tetrachloride has a higher boiling point because the dispersion forces are extensive enough to be stronger than the dipole-permanent dipole interactions in chloroform.

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