Download
1 / 38
380 likes | 584 Vues
Exam 3 Review. Chapters 8, 9, and 10. Format of exam. 20 multiple choice questions – 200 points Once again, there will be a 30 minute time limit on this. 5 problems – 300 points 2 problems dot structures, geometry, etc. 3 gas law problems Bonus problem – 50 points. 1. Lattice energy is:.
E N D
Exam 3 Review Chapters 8, 9, and 10
Format of exam • 20 multiple choice questions – 200 points • Once again, there will be a 30 minute time limit on this. • 5 problems – 300 points • 2 problems dot structures, geometry, etc. • 3 gas law problems Bonus problem – 50 points
A • This is the definition of lattice energy. See Section 8.2
2. For a given arrangement of ions, the lattice energy increases as ionic radius __________ and as ionic charge __________.
A • Once again, see section 8.2.
3. Which of the following has the largest lattice energy? • CsI • CsF • MgO • MgS • LiI
C • MgO has the smallest ions, and largest charges. See section 8.2
4. Elements from opposite sides of the periodic table tend to form __________.
B • This is kind of scattered throughout the course so far! See the first page of Chapter 8, and the beginning of Section 8.3.
B • Remember, transition metals lose their “s” electrons before the “d” electrons when forming ions (a good piece of “chemistry trivia” to know…)
6. Which order is correct for increasing polarity (least polar first)? Si-Cl S-Cl P-Cl Si-Si • Si – Cl < S – Cl < P – Cl < Si – Si • Si – Si < P – Cl < S – Cl < Si – Cl • Si – Si < S – Cl < P – Cl < Si – Cl • Si – Si < P – Cl < S – Cl < Si – Cl
C • See section 8.4 – you need to be able to do this by just looking at a periodic table (not at a table of electronegativity values).
The formal charge of each atom in an ion of SO32- is: • S = 0, O = 0 • S = 0, O = 2- • S = 2-, O = 0 • S = 1+, O = 1- • S = 1-, O = 1+
D • Formal charge is [valence electrons – “assigned” electrons]. You need to draw the dot structure of the molecule before you can answer this question! See p.307-308.
8. As the number of covalent bonds between two atoms increases, the distance between the atoms __________ and the strength of the bond between them __________.
D • See Section 8.2
9. What is the fundamental idea behind VSEPR theory? • Molecular geometry is determined by the number of electrons in a molecule. • Electron pairs in a molecule arrange themselves to minimize electron-electron repulsions. • Non-bonding regions of electrons take up more space in a molecule than bonding regions.
B • You might want to read sections 9.1 and 9.2 if you didn’t know this.
10. Of the following, only __________ has sp2 hybridization of the central atom.
B • You need to draw the dot structure to get this correct…
11. There are __________ σ bonds and __________ π bonds in H3C–CH2–CH=CH–CH2–C≡CH. • 10, 3 • 12, 2 • 13, 2 • 16, 3
D • Every single bond is a σ bond, as is the first part of a multiple bond. A double bond has one σ bond and one π bond…a triple bond has σ bond and two π bonds. It’s probably helpful to draw this whole molecule out (so you get each C – H bond).
12. If the temperature of a fixed volume of gas is doubled, what will happen to the pressure of the gas? • It will also double • It will be cut in half • There is no way to predict this without knowing the specific values involved.
A • This is actually a statement of Gay-Lussac’s law (which is not explicitly stated in your text). It should make sense, or you can see this relationship from the ideal gas law.
13. You have four 1-L rigid containers that each contain 1 mole of He, Ne, Ar, and Kr at 300K. The atoms in which container have the highest average kinetic energy? • He • Ne • Ar • Kr • They’re all the same
E • It’s a “trick question” (well, not really). The average kinetic energy of a gas is directly proportional to temperature – as long as they’re all at the same temperature, they have the same average kinetic energy. The He atoms will have the highest velocity among them, however, as they are the lightest.
14. At 333 K, which of the pairs of gases below would have the most nearly identical rates of effusion?
B • Since these two gases have almost the same molar mass, you would expect them to have similar rates of effusion (section 10.8) You might also want to think about which has the highest rate of effusion (or lowest…)
15. The ideal gas law ignores which physical characteristics of gases? • The finite volume of the gas molecules • The attractive forces between gas molecules • The density of gases • Both A and B • All of the above
D • Read section 10.9 (really!!)
16. At what conditions will the ideal gas law fail? • High temperature and low pressure • High temperature and high pressure • Low temperature and low pressure • Low temperature and high pressure
D • Another place to reference section 10.9 – and be sure that you can tie in how this relates to the previous question in this review…
17. The volume of a sample of gas (2.49 g) was 752 mL at 1.98 atm and 62°C. The gas is __________.
D This will NOT be a multiple choice question…a little preview of another problem. Calculate the molar mass first.
0.900 g/L • One more time, this will NOT be a multiple choice question…a little preview of another problem.
