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1. Using a Table of Electronegativity values, what type of bonding will the following compounds have? Explain your answer. a. O2
Non-polar covalent bond (zero electronegativity difference) 2. Without using a Table of Electronegativity values, what typing of bonding will be in each of the following. Explain your answer. a. CS2 polar
covalent bonds because 2 different nonmetals 3. Without using a table of Electronegativity values, circle the element that you would expect to be more electronegative of the two listed. What does this mean to be more electronegative? a. O
or S because the electronegativity decreases going down a column 4. On scratch paper, make Lewis Electron Dot diagrams for the molecules listed. Then fill in the table indicating shape and polarity.
5. Draw Lewis Electron Dot structures for the following polyatomic ions. Then list the shape of each. (Note that since these are ions they will be ionically bonded to another ion not listed in the problem. So remember you are just drawing “half” of a compound.) a. PO4
–3 Tetrahedral shape 6. Draw Lewis electron dot structures for the following diatomic molecules. Then list whether each has a single, double or triple bond between atoms. a. N2
Triple bond 7. Sketch the electron dot structure for carbonate, CO3-2 and sulfite SO3-2. For each one, list the number of bonding and non-bonding (lone pairs) electrons on the central atom. How does this affect their shapes? (I can’t do the sketches on the computer) The carbonate has 3 “things” around it. There is one double bond and two single bonds and 0 lone or nonbonding pairs around the central carbon. But because there are no lone pairs the shape is triangular planar. The sulfite has 4 “things” around it, three bond pairs (all single bonds) and one lone pair (or nonbonding pair) around the S. This makes it pyramidal. 8. The molecule NF3 has polar bonds and is a polar molecule whereas the molecule CF4 also has polar bonds but is a non-polar molecule. Explain why this statement is true. NF3 has polar bonds because of a 1.0 electronegativity difference between the N and F. It is a pyramidal shape. Because it is not symmetrical the electrons are pulled more towards the F’s which makes them all slightly negative and the N slightly positive. A dipole is produced which means it is like a little magnet with a positive and negative side. CF4 has polar bonds also because a 1.4 electronegativity difference between the C and F. It is a tetrahedral shape. Since F is more electronegative, the negative charge will be pulled towards every F, but since it is symmetric overall it has equal distribution of charge and thus no dipole is set up. 9. Name the following covalent compounds: a. SO2
Sulfur dioxide 10. Using your own words explain the significance of a “mole” and why Avogadro would have wanted to calculate it. The atomic masses were originally just the relative masses (common term is weight) of one element compared to another. The mass depends on the number of protons and neutrons in the nucleus. Avogadro calculated the number of atoms that would be in the element if the unit “grams” were used. For example the atomic weight of Helium is 4.0 so if we use the unit “gram”, a mole or Avogadro’s number is the number of atoms in 4.0 grams of He. Since Ne is heavier (20.18 grams) a mole would represent the number of atoms in 20.18 grams of Ne. A mole turns out to be 6.02 x 1023. 11. What is the formula mass of a. HF
20.0 g (note, I am using one decimal point in the answers) 12. Complete these calculations by filling in the blanks a. 1 dozen
books = 12 books = 24 pounds *Note: for (d) this is equal to 18.06 x 1023 but is not is simplest form. Also for (f) you could say 12.04 x 1023 but this is also not in simplest form 13. a. How many grams are in 3 moles of He? 12.0 grams b. If you have 60.3
grams of Ne, how many moles and how many atoms 14. Given the balanced equation for the rusting of iron: Fe (s) + O2 (g) ® Fe2O3 (s) + E a. State what
the reaction means in words, including the meaning of each 4Fe (s) +3 O2 (g) ® 2Fe2O3 (s) + E 4 moles 3 moles 2 moles 223.6 g 96.0 g 319.6 (Note: I rounded to one decimal place. If you carry more or less decimal places than that you will have slightly different numbers) e. Set up a ratio of the number of grams of iron that will react with oxygen.
The mole ratio is 4 iron/3 oxygen but the gram
ratio is 15. Balance these equations: a. 4Al +
3O2 ®
2Al2O3 16. What is the difference between kinetic and potential energy? Compare and contrast the KE and PE in solids, liquids and gases. KE is energy of motion and PE is energy of position or stored energy. Gases have more KE because they have the most motion whereas solids have the least. Solids have the most PE because the energy is stored in the forces holding them together. Since gases have the least forces holding them together they have the least PE. 17. Maria is pushing her little sister on a swing. Explain the position of the swing where it has the most PE and the most KE. When the swing is at the highest point at switching from one direction to go back, it has the most PE. It has the most KE at the lowest point when it is actually moving the most quickly. The two go back and forth as the swing moves. If KE is going up, PE is going down and vs versa. 18. Which state of matter a. has the
greatest density? Usually solids 19. Explain why a gas expands when heated. When a gas is heated the particles have more energy and move more quickly. This causes them to take up more space, and if you don’t let it expand the pressure would build because that energy has to go somewhere. 20. Compare and contrast a solid and liquid using the Kinetic theory. Solids have greater forces of attraction between the particles and thus have more PE. There is some vibrational movement but it is way less than liquids or gases. Gases have more KE because they are moving more quickly and colliding into each other. They have far less attractive forces between particles than a liquid or solid.
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