Principles of Chemistry IICHEM 1212Chapter 11
1. List the different phase transitions that are possible and give examples of each.
2. Describe vapor pressure in molecular terms. What do we mean by ‘it involves a dynamic equilibrium’.
3. Explain what is meant by hydrogen bonding. Describe the hydrogen bonding between two H2O molecules.
4. Which elements can take part in hydrogen bonding?
5. Explain the following terms and give an example of each:
a) dipole-dipole interactionb) London dispersion forcesc) van der Waals forces
6. What type of physical properties would you have to consider in comparing the strength of intermolecular forces in solids and in liquids.
7. What is the difference between intermolecular forces and intramolecular forces? Which is stronger? Give two examples of each.
8. Why is heat of fusion of a substance smaller than heat of vaporization?
9. Describe the behavior of a liquid and its vapor in a closed vessel as the temperature increases.
10. Consider a substance X with a ΔHvap = 20.3 kJ/mol and ΔHfus = 9.0 kJ/mol. The melting point, boiling point, and heat capacities of both the solid and the liquid X are identical to those of water (ΔHvap = 44.0 kJ/mol and ΔHfus = 6.01 kJ/mol).If you place one beaker containing 50 g of X at -10 oC and another beaker with 50 g of H2O at -10 oC on a hot plate and start heating them:
a) which material will reach the boiling point first?
b) which material will completely boil off first?
Sketch the heating curves for H2O and X. How do the heating curves reflect your answers from parts a and b?
11. The compounds Br2 and ICl have the same number of electrons, yet Br2 melts at -7.2 oC, whereas ICl melts at 27.2 oC. Explain.
12. The binary hydrogen compounds of group 4A elements are CH4 (-162 oC), SiH4 (-112 oC), GeH4 (-88oC), and SnH4 (-52oC). The temperatures in parenthesis are the corresponding boiling points. Explain the increase in boiling points from CH4 to SnH4.
13. List the type of intermolecular forces that exist between molecules (or basic units) in each of the following species: C6H6, CH3Cl, PF3, NaCl, CS2
14. Arrange the following in order of increasing boiling points:RbF, CO2, CH3OH, CH3Br. Explain your choice.
15. What kind of attractive forces must be overcome in order to:
a) melt iceb) boil molecular brominec) melt solid iodined) dissociate F2 into F atoms
16. Explain surface tension. What is the relationship between the intermolecular forces that exist in a liquid and its surface tension?
17. Use water and mercury as examples to explain adhesion and cohesion.
18. Why is ice less dense than water?
19. Outdoor water pipes have to be drained or insulated in winter in a cold climate. Why?
20. The triple point of a compound Z is -5.1 oC at 3.3 atm and the critical point is 51 oC and 99.1 atm. Sketch the phase diagram for the compound Z. What is the state of Z at a temperature and pressure of 48 oC and 1 atm? If the temperature is reduced to -10 oC while maintaining the pressure at 1 atm, what would be the state of Z?
21. Predict the order of increasing vapor pressure at a given temperature for the following compounds: FCH2CH2F, HOCH2CH2OH, FCH2CH2OH. Explain your reasoning.
22. Which of the following do you expect to be molecular solids: NaOH, solid C2H6, nickel?
23. Which of the following are molecular solids and which are covalent solids? Se8, CO2, I2, HBr, Si, C, B, SiO2, SiC, BN,
24. How many atoms are in a i) simple cubic unit cell ii) body-centered cubic unit cell iii) face-centered cubic unit cell, of an atomic crystal in which all atoms are at lattice points? What is the coordination number in each case, assuming all spheres are of equal size? Sketch the crystal structure of each kind of unit cell and clearly show all lattice points with spheres.
25. The distance between layers in a NaCl crystal is 282 pm. X-rays are diffracted from these layers at an angle of 23.0o. Assuming that n = 1, calculate the wavelength of the X-rays in nm.(0.220 nm)
26. Copper metal has a face-centered cubic structure with all atoms at lattice points and a density of 8.93 g/cm3. Its atomic mass is 63.5 g/mol. Calculate the edge length of the unit cell.(3.61 x 10-8 cm)
27. Gold has cubic crystals whose unit cell has an edge length of 407.9 pm. The density of the metal is 19.3 g/cm3. From these data and the atomic mass, calculate the number of gold atoms in a unit cell, assuming all atoms are at lattice points. What type of cubic lattice does gold have?(4 atoms, FCC)
28. Tungsten has a body-centered cubic lattice with all atoms at lattice points. The edge length of the unit cell is 316.5 pm. The atomic mass of tungsten is 183.8 g/mol. Calculate its density.(19.26 g/cm3)
29.Lead has a face-centered cubic lattice with all atoms at lattice points. The edge length of the unit cell is 495.0 pm. The atomic mass of lead is 207.2 g/mol. Calculate its density. (11.35 g/cm3)