Intermolecular Forces

Question 1

What is the difference between inter and intramolecular force?

Answer 1

Inter is between molecules and intra is within molecules

Question 2

Where do intermolecular forces originate?

Answer 2

Interactions between charges, partial charges, and temporary charges

Question 3

What is stronger intermolecular forces or bonding forces?

Answer 3

Bonding forces

Question 4

What is an ion-induced dipole force?

Answer 4

When an ion approaches a non polar molecule it creates a small induced dipole

Question 5

What does the magnitude of ion-induced dipole depend on?

Answer 5

Charge of ion and the polarizability of the atom (how easy electrons move), polarizabilty also depends on size of electron cloud

Question 6

What intermolecular force is present in all neutral atoms?

Answer 6

Dispersion force (LDF)

Question 7

What is a dispersion force?

Answer 7

Electrons are not always uniformly distributed, sometimes creates small positive and negative end

Question 8

What does an instantaneous dipole on atom atom do?

Answer 8

Induces dipoles on neighboring atoms which attract each other

Question 9

What types of molecules have stronger dispersion forces?

Answer 9

Molecules with a lot of electrons and ones that are elongated (more space for interaction)

Question 10

What force exists in all polar molecules?

Answer 10

Dipole-dipole

Question 11

What are dipole dipole forces?

Answer 11

Permanent dipole caused by difference in EN

Question 12

What is the effect on the boiling point as the dipole moment increase?

Answer 12

Boiling point increases

Question 13

Will a polar liquid mix with another polar liquid? What about non polar!

Answer 13

Yes

No

Question 14

What are hydrogen bonds?

Answer 14

Hydrogens bound directly to a highly electronegative atom can form weak bonds with the atom in a adjacent molecule

Question 15

What atoms does hydrogen bonding occur with?

Answer 15

Hydrogen and fluorine, oxygen, and nitrogen

Question 16

What is dipole induced dipole force?

Answer 16

The force between molecules with a permanent dipole and a non polar one

Question 17

What is ion dipole force?

Answer 17

Occur when an ionic compound is mixed with a polar compound, important for aqueous solutions of ionic compounds

Question 18

What is the strongest intermolecular force?

Answer 18

Ion dipole force

Question 19

Where is dipole induced dipole forces present?

Answer 19

Non polar molecules mixed with polar ones

Question 20

Where is ion induced dipole force found?

Answer 20

Dilute mixture of ionic compound and non polar substance

Question 21

How do you solve a problem when you are given the mass of a liquid and a solid block and the initial temperature, when the energy released during condensation only warms the block and you need to find final temperature?

Answer 21

Find the heat of liquid in joules using mass, molar mass, and energy of vaporization

Then make the heat of block equal to negative heat of liquid

Solve for final temperature

Question 22

Why do liquids tend to minimize surface area?

Answer 22

Molecules at surface are less stable and it takes energy to move a molecule from interior to surface

Question 23

What is surface tension?

Answer 23

Energy required to increase the surface area

Question 24

What happens to surface tension as intermolecular forces decrease?

Answer 24

It decreases

Question 25

What is viscosity? What is the SI unit?

Answer 25

Resistance of a liquid to flow Pa s

Question 26

What are viscosity trends?

Answer 26

Increases with increasing intermolecular forces, increased with a longer molecule shape, decreases with temperature

Question 27

What is capillary action? What is it the result of?

Answer 27

Ability of a liquid to flow against gravity up a narrow tube Cohesive and adhesive forces

Question 28

How does temperature affect vaporization?

Answer 28

At a lower temperature less molecules have the minimum KE to escape into gas phase At a higher temperature more molecules have a high enough energy to evaporate

Question 29

What happens in a closed container in terms of condensation and evaporation?

Answer 29

Reaches equilibrium

Question 30

What does the rate of vaporization increase with?

Answer 30

Temperature, surface area, and decreasing inter molecular forces

Question 31

What is the enthalpy of vaporization? Is it endo or exothermic?

Answer 31

Amount of heat required to vaporize one mole of a liquid to gas Endothermic (always positive)

Question 32

What is the enthalpy of condensation equal to?

Answer 32

Negative enthalpy of vapourization

Question 33

How can you find the mass of something that can be vaporized at its boiling point when given heat?

Answer 33

Rearrange enthalpy=q/mol and then convert to grams

Question 34

What is dynamic equilibrium? What happens when system is disturbed?

Answer 34

Rate of vaporization equals rate of condensation Systems try’s to minimize the disturbance and return to equilibrium

Question 35

What is the normal boiling point? What is the standard boiling point?

Answer 35

The temperature when the vapor pressure is equal to one atmosphere The temperature where the vapor pressure equals one bar

Question 36

If you are given the heat of vaporization and the temperature of the normal boiling point and are asked to find the vapor pressure at a given temperature what can you use?

Answer 36

In(P2/P1)=-deltaHvap/R (1/T2-1/T2)

Question 37

How can you get rid of a natural log?

Answer 37

Raise to e^In

Question 38

What is the critical point?

Answer 38

When the distinction between liquid and vapor disappears

Question 39

What is the enthalpy of sublimation?

Answer 39

Enthalpy of fusion + enthalpy of vaporization

Question 40

What is sublimation vs deposition?

Answer 40

Solid to gas Gas to solid

Question 41

What is fusion? What is the enthalpy of fusion equal to? What is the opposite?

Answer 41

Solid to liquid(Melting), heat of fusion, liquid to solid (freezing)

Question 42

Is enthalpy of fusion positive or negative? What about enthalpy of freezing?

Answer 42

Positive, opposite sign of fusion but same magnitude

Question 43

How can you calculate a heating curve for water?

Answer 43

1. Heating solid ice (use q=mcdeltaT) 2. Going from solid to liquid (use q=n x enthalpy of fusion) 3. Heating liquid water (use q=mcdeltaT) 4. Going from liquid gas (use q=n x enthalpy of vaporization) 5. Heating steam (use q=mcdeltaT)

Question 44

What are molecular solids?

Answer 44

Crystalline solids composed of molecules, held together by intermolecular forces (dispersion, dipole dipole, hydrogen), low melting points

Question 45

What are ionic solids?

Answer 45

Solids made up of ions, held together by interactions between cations and anions

Question 46

What are atomic solids?

Answer 46

Made up of individual atoms Non bonding, held together by weak dispersion forces, noble gases in solid form Metallic, held together by metallic bonds and de localized molecular orbitals Network covalent, held together by covalent bonds, sort of like giant molecules