You think you know; but do you really know…

1. Are you familiar with the various types of intermolecular bonds? Y or N?

You think you know; but do you really know…

2. Can you differentiate which would be the dominant force of attraction in various situations comparing molecules? Y or N?

You think you know; but do you really know…3. What would the dominant force of attraction be in each of the following situations?A. Two polar molecules with small and similar molar masses that do not contain hydrogen…

Dipole-Dipole

You think you know; but do you really know…3. What would the dominant force of attraction be in each of the following situations?B. Two polar molecules

with small and similar molar masses; one containing hydrogen…

Dipole-Dipole and perhaps H-bonding!

You think you know; but do you really know …3. What would the dominant force of attraction be in each of the following situations?C. Two polar molecules with small and similar molar masses; one containing hydrogen bonded to nitrogen the other to chlorine. (note Cl and N have identical E.N.’s)H-bonding!

You think you know; but do you really know …

3. What would the dominant force of attraction be in each of the following situations?

D. Two nonpolar molecules that may or may not contain hydrogen but definitely do not contain N, O or F.

LDF

You think you know; but do you really know …

4. Draw a 3-d Lewis Diagrams for dimethyl ether and ethyl alcohol. Then determine which has the highest boiling point.

Did you really know?????

dimethyl ether CH3OCH3

ethyl alcohol C2H5OH

vp

K.E.Threshold energy needed for

particles to breakaway

increases in number with higher temp.

rate

time

condensation

evaporation =

# of particles above the liquid is constant; vapor pressure can be measured.

Particles with enough energy to break away

(higher at higher temp.s) temp

ln vp

1 / T

ln vp = (-Hv/R)(1/T) + Cln (vp1/vp2) = (Hv/R)(1/T2-1/T1)

The Clausius- Clapeyron Eq.

ln vp1 = (-Hv/R)(1/T1) + C

ln vp2 = (-Hv/R)(1/T2) + C

ln vp1 - (-Hv/R)(1/T1) = C

ln vp2 - (-Hv/R)(1/T2) = C

# of

par

ticle

s

ln vp2 - (-Hv/R)(1/T2)

ln vp1 - ln vp2= (Hv/R)(1/T2) - (Hv/R)(1/T1)

Calculate the enthalpy of vaporization and the normal boiling point of methanol using the following data:

Temp.(°C) V.P. (in mm Hg)

-6.0 20.0

5.0 40.0

12.1 60.0

21.2 100.0

Calculate the enthalpy of vaporization and the normal boiling point of methanol using the following data:

Find Hv by manipulation of C-C equation:

Hv = ln(vp1/vp2) R (1/T2 – 1/T1)

Hv = ln(40mm/60mm)8.31J/mol K

(1/285.1 K – 1/278 K)

Hv = -3.37J/mol K

(-8.96 x 10-5 K)

Hv = 37600 J/mol

Hv = 37.6 kJ/mol

Calculate the enthalpy of vaporization and the normal boiling point of methanol using the following data:

Temp.(°C) V.P. (in mm Hg)

-6.0 20.0

5.0 40.0

12.1 60.0

21.2 100.0

Calculate the enthalpy of vaporization and the normal boiling point of methanol using the following data:

Find B.P. by manipulation of C-C equation:

ln(vp1/vp2) R = (1/T2 – 1/T1)

Hv

ln(40mm/760mm)R = (1/T2 – 1/278.0 K)

37600 j/mol

(-0.0000783)R = (1/T2 – 1/278.0 K)

-0.000651 K = (1/T2 – 0.00360 K)

0.00295 K = 1/T2

339 K = T2

339 - 273 = 66° C = T2 = B.P.

Equilibrium Vapor Pressure Curve for Water

Boiling occurs when the vapor pressure of a liquid is equal to the atmospheric pressure.…the boiling pointboiling point is the temperature at which this occurs.