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You think you know; but do you really know…

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….

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You think you know; but do you really know…

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  1. You think you know; but do you really know… 1. Are you familiar with the various types of intermolecular bonds? Y or N?

  2. 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?

  3. 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

  4. 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!

  5. 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!

  6. 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

  7. 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. dimethyl ether CH3OCH3 ethyl alcohol C2H5OH Did you really know?????

  8. # of particles Particles with enough energy to break away increases in number with higher temp. K.E. Threshold energyneeded for particles to breakaway evaporation = rate condensation time ln vp1 = (-DHv/R)(1/T1) + C # of particles above the liquid is constant; vapor pressure can be measured. ln vp2 = (-DHv/R)(1/T2) + C vp ln vp1 - (-DHv/R)(1/T1) = C ln vp2 - (-DHv/R)(1/T2) (higher at higher temp.s) ln vp2 - (-DHv/R)(1/T2) = C ln vp1 - ln vp2= (DHv/R)(1/T2) - (DHv/R)(1/T1) temp ln vp ln vp = (-DHv/R)(1/T) + C ln (vp1/vp2) = (DHv/R)(1/T2-1/T1) The Clausius- Clapeyron Eq. 1 / T

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

  10. Find DHv by manipulation of C-C equation: DHv = ln(vp1/vp2) R (1/T2 – 1/T1) DHv = ln(40mm/60mm)8.31J/mol K (1/285.1 K – 1/278 K) DHv = -3.37J/mol K (-8.96 x 10-5 K) DHv = 37600 J/mol DHv = 37.6 kJ/mol

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

  12. Find B.P. by manipulation of C-C equation: ln(vp1/vp2) R = (1/T2 – 1/T1) DHv 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.

  13. Equilibrium Vapor Pressure Curve for Water Boiling occurs when the vapor pressure of a liquid is equal to the atmospheric pressure. …the boiling point is the temperature at which this occurs.

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