Chapter 12 Notes Test Questions – Flashcards

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question
What are the Strong IMF's?
answer
high boiling point, high melting point, high ;Hvap, high ;Hfus, high ;Hsub, low VP
question
What are the weak IMF's?
answer
low boiling point, low melting point, low ΔHvap , low ΔHfus, low ΔHsub, high VP
question
what is a dipole-dipole force?
answer
a positive and a negative end of another molecule are attracted to each other
question

which of the following molecules have dipole-dipole forces?

a) CO2

b) CH2Cl2

c) CH4

d) Cl4

e) CH3Cl

f) HCl

answer

a) CO2               no

b) CH2Cl2          yes

c) CH4               no

d) Cl4                no

e) CH3Cl          yes

f) HCl                yes

question
what is an ion-dipole force?
answer
the attractive forces between an ion and a polar molecule
question
Which should have more negative hydration energy, Cl- or Br-?
answer
Br- is larger than Cl- so Cl- has the more negative ΔH hydration
question
what is a London Dispersion force?
answer
present in all molecules
question

what type(s) of intermolecular forces exist between each of the following molecules?

a) HBr

b) CCl4

c) PF3

d) PCl5

e) SO2

f) CS2

g) H2S

answer

a) HBr = dispersion forces, dipole-dipole forces

b) CCl4 = dispersion forces

c) PF3 = dispersion forces, dipole-dipole forces

d) PCl5 = dispersion forces

e) SO2 = dispersion forces, dipole-dipole forces

f) CS2 = dispersion forces

g) H2S = dispersion forces, dipole-dipole forces

question
what is a hydrogen bod?
answer
a dipole-dipole interaction between the hydrogen atom in a polar N-H, O-H, or F-H bond and an electronegative O,N, or F atom
question

Which of the following exhibits significant hydrogen bonding?

a) HBr

b) H2CF2

c) H2

d) CH3CN

e) CCl4

f) CH3CO2H

g) CH3COCH3

h) H2S

i) CH3CH2OH

answer

a) HBr = no

b) H2CF2 = no

c) H2 = no

d) CH3CN = no

e) CCl4 = no

f) CH3CO2H = yes

g) CH3COCH3 = no

h) H2S = no

i) CH3CH2OH = yes

question
what is vapor pressure?
answer
the pressure of a vapor above a liquid at a given temperature
question
what is vaporization?
answer
the phase change from liquid to vapor
question
what is condensation?
answer
the phase change from vapor to liquid
question
The molar enthalpy of vaporization of water is 40.7 kJ/mol at 100oC. How much energy is required to vaporize 925g of water at 100oC? (H2O = 18.02g/mol)
answer

g --> mol --> kJ

925g x (1mol H2O/18.02g) x (40.7kJ/1mol H2O)

= 2.09 x 103kJ

question
Calculate the mass of water that can be vaporized at its boiling point with 155kJ of heat. (ΔHvap = 40.7kJ/mol)
answer

kJ --> mol --> g

155kJ x (1mol H2O/40.7kJ) x (18.02g/1mol)

= 68.6g H2O

question
what is the Clausius-Clapeyron equation?
answer

ln (P2/P1) = - (ΔHvap/R)(1/T2 - 1/T1)

 

R = gas constant (8.314 J/K mol)

question

The vapor pressure of benzene C6H6, is 40.1mmHg at 7.6oC. What is the vapor pressure at 60.6oC?

(ΔHvap = 31.0kJ/mol)

answer

ln (P2/P1) = - (ΔHvap/R)(1/T2 - 1/T1)

ln (P2/40.1mmHg) = - (31.0kJ/mol/8.314x10-3kJ/K mol)(1/333.6K - 1/218.6K)

ln (P2/40.1mmHg) = 2.11 (take the antilog of both sides)

P2/40.1mmHg = e2.11

P2 = e2.11 x 40.1mmHg

P2 = 331mmHg

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