H CH 7 HOMEWORK
Draw Lewis Structures for the following:
Single Bonds

H
2
O*, C
2
H
6
, CCl
4
*
Double Bonds  CH
2
O*, CO
2
*, COCl
2
Triple Bonds

C
2
H
2
Polyatomic Ions

NH
2
-1 *, CN -1 , NO
3
-1 *
Miscellaneous

H
2
O
2
, CS
2
*, CO, N
2
H
2
, O
3
*, N
2
F
4
, IO
3
-1 *, HCN*, N
2
O*, SiO
4
-4*
Determine the shape, bond angle, polarity, type of hybridization, and the number of σ and
π bonds of the above compounds with an (*) beside them.
Review:
1.
What is the relationship between electronegativity difference and bond type?
2.
What is the meaning of the term polar as applied to chemical bonding?
3.
What one thing will determine if atoms will form chemical bonds?
4.
What is meant by an unshared or lone pair of electrons?
5.
Determine the number of valence electrons in each of the following:
H Mg Al F N Ne C O
6.
What is an ionic compound?
7.
In what form do most ionic compounds occur?
8.
What is a formula unit? How many K
+1 and S
-2 ions would be in one formula unit of the ionic compound formed by these ions?
9.
In general, how do ionic and molecular compounds compare in terms of physical properties?
10.
What is a metallic bond?
11.
What are hybrid orbitals?
12.
What are intermolecular forces?
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13.
List the three intermolecular forces and describe them.
14.
What 2 things determines the polarity of a molecule?
15.
Determine the resulting bond type and draw the dipole (if applicable) for each of the following if bonded together.
H and I Ba and S Br and K
Zn and O I and N S and I
18. How many sigma and pi bonds would be in a molecule of COCl
2
?
19. Use orbital notation to show the bonding in H
2
O
2
, CS
2
, and KCl.
20. What group would element “X” belong to: (Assume that all atoms have an octet.)
X—Br X—X—X (-2 on entire structure)
21. Do the following represent resonance structures or structural isomers?
O
||
H—C AND
O
|
H—C
| ||
O O
22. What type of hybridization is represented in the molecules in #21?
23. Draw the Lewis structure for SF
4.
24. Which of the following sets of molecules would exhibit stronger Van der Walls forces and why?
|
A) X—X—X—X—X
-----------------------
X X X X
B) \ / | \ /
X X
X—X—X—X—X / \ | / \
X X X X
|
25. . An article in the Journal of Chemical Education was entitled "Solving the Mystery of
Fading Fingerprints." It dealt with a crime where an 8-year-old girl was kidnapped in the south during the summer and eventually escaped. The kidnapper was finally caught four days later but when his car was searched for fingerprints of the victim, all that was found were fingerprints from the kidnapper. Fingerprints consist primarily of water, but also contain oils (carbon chains), fatty acids (carbon chains), esters (carbon chains), salt, urea, and amino acids. What is a possible explanation for the reason that the girl's fingerprints were not found in the car but his were? Yes, she was in the car and did touch parts of the car and yes, she also has hands
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H LAB: TYPES OF BONDS
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Melting Point:
1.
Obtain an Aluminum dish and place a small amount of each of the 5 compounds around the dish. Make sure they are an equal distance away from the center of the dish.
2.
Make sure to label where each of the 5 compounds is located on the dish.
3.
Set up the apparatus as shown in figure 1.
Figure 1
4.
Light the candle and place it under the middle of the aluminum dish. Make sure that the flame is touching the bottom of the dish.
5.
Allow the candle to heat the compounds for 5 minutes and record your qualitative observations.
Solubility:
NOTE: LIKE THINGS DISSOLVE LIKE THINGS.
1.
Obtain 5 test tubes and a test tube rack. Clean the test tubes and place them on the rack.
2.
Using a pipette, add 2 ml of water to each of the five test tubes.
3.
Add a small amount of each of the five compounds to separate test tubes and agitate each for
30 seconds.
4.
Observe whether the solute (the thing being dissolved) dissolves in the solvent (the thing doing the dissolving).
Conductivity:
1.
Place a small amount of each of the five compounds in five separate beakers each containing
150 ml of water.
2. Use the conductivity tester to see if the compound will conduct electricity in solution.
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H LAB: CHROMATOGRAPHY
1.
Obtain a piece of chromatography paper.
2.
Draw a horizontal pencil line across the short side of the paper between 1 and 2 cm from the bottom.
3.
Place black dots on the line from the different markers. Space them evenly apart.
Make sure to indicate the name of the marker in pencil for each dot. Do not draw on the paper, just press the marker gently against the paper and the ink will be drawn out of the marker.
4.
Fold your piece of paper in half parallel to the long side of the paper and make a
90

angle. Place the paper in a 250 ml beaker containing 5 ml of water. Make sure that the level of the liquid is below the pencil line.
5.
Obtain an unknown ink sample and draw a horizontal line through it across the paper. Place this paper in the beaker with the other chromatograph.
6.
Leave the papers in the beaker for approximately 20 minutes.
7.
Remove the paper and immediately draw a pencil line across the paper where the water has stopped.
8.
Allow the chromatograph to dry.
Questions and Calculations:
1.
Determine the R f
(Retention Factor) value for each color in each marker. Do both the known and unknown samples. Watch sig figs. (5 pts)
Distance the ink traveled
R f
= ----------------------------------------
Distance the solvent traveled
2.
Determine what unknown you have. Give specific qualitative and quantitative data to support your choice. (2 pt)
3.
Which of the markers uses a nonpolar solvent to transfer the ink? Explain.
(2 pts)
4.
In general, which pigment seems to have the largest net dipole for the Eberhard Faber
(EF) marker? Which one has the smallest net dipole? Explain. (3 pts)
5.
Is the yellow pigment in the Eberhard Faber marker the same yellow pigment that is in the LiquiMark marker? Explain. (3 pt)
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