G.C.1-10 Lab Report-2 - chemistry lab course work. PDF

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G.C.1-10 Lab Report Name: Stephanie Sandler Z Number: Z23552088 Lab TA’s Name and Section Number: Guilherme Da Silva / Section 4 A statement Accountability: “I certify that this is my own work, and I understand that if I am found to be in violation of the honor code, I will be subject to the highest penalty.” SUMMARY When you are looking at molecular models, there are two general ideas. There’s a ball and stick model and a wireframe model. The ball and stick is a very simple model because it’s popular in introductory organic chemistry and it has balls that are representative of atoms and sticks that are bones. So you just make bones by inserting in the premade holes, and you make a carbon hydrogen bone. For example, if you want to make methane that looks like carbon and hydrogen x4 (CH4), you do this 4 times and end up with methane. You can see it’s a tetrahedral shape and corresponds to these four. If you want to make ethane, which has carbon x2 bond and has CH3 x2, you do the same thing as well. A carbon x2 double bond on paper is ethylene and you want to build it with your models. You use still the normal sticks for the carbon hydrogens, but to make the double bond, you need to use the flexible ones. So you can actually take these two CH3 and you insert them like that; so you get one bond and make the second bond then you bend it and end up with ethylene. To make a triple bond, you can do the same thing. You just make a second one that looks like the last example. Now the hydrogens are sticking out 180o. There’s a saying if you draw the two tetrahedral by vertex, you make a carbon x2 bond, making ethane. If you want to make a carbon x2 double bond, you would join these vortexes and these vortexes, so they’re joined through an edge and that’s the bond for you. If you want to make a carbon triple bond, you have one, two, and three vortexes, so they are attached by a face and you have the 2 hydrogens sticking out like that. The wireframe models are based on Pauling’s hydrogenation idea. If you see you have a lot of different pieces and they have written on the arm saying SP-3, you can separate the carbon in SP-3 as always. Carbon makes 4 bonds and this piece has only 2, so you have to join two together and they will snap like that to make methane. If you want to make ethane, let’s say it’s CH3, you join two of them and then you can simply make the carbon x2 bond like that and that’s the equivalent of the examples shown. If you want to make a double bond, now you have to use different pieces. You take a double bond piece and an SP-2 carbon and put them together to make ethane. The main problem with this way of presentation is that the angles inside the hydrogen carbon hydrogen bond are fixed at 109o, which is the right angle. While if you want to make ethane, these angels should be 120o because they’re 360 divided by 3. So the first angle is too small and these models are good for very simple molecules, but they won’t really be accurate enough

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when you start building up. While the other one is 120o and a lot more faithful to the right bond angle. For example, if you make benzine, that’s 6H6, which is 6 hydrogen with 3 double bonds in it. There’s lots of advantages and disadvantages to both of these types of models.

Part I. Hydrides and Periodicity 1. Determine the formulas of the hydrides of the following atoms: C, N, O, F, Si, P, S, Cl 2. Write these formulas in the appropriate place in Table 1 of your lab report. 3. Complete Table 1 by determining the number of valence electrons and Lewis Structures of the hydride compounds. 4. Determine the electron pair and molecular geometries of these compounds. Record your findings in Table 2 of your lab report.

Part II. Fluorinated Compounds 5. Determine the electron pair and molecular geometries of the fluorinated compounds shown in Table 3. Record your findings in Table 3.

Part III. Hydrocarbons 6. Draw a Lewis structure of methane, CH4. 7. Draw the Lewis structures of ethane, C 2H6 and propane, C3H8. 8. Draw Lewis structures of butane, C4H10. 9. Enter the appropriate information in Table 4, and answer the appropriate questions in the laboratory report.

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Part I: Hydrides and Periodicity Table 1: Lewis Structures of Hydrides Central

Formula Of

Total # of Valence

Atom

Hydride

Electrons

CH4

8

NH3

8

H2O

8

HF

8

C

N

O

F

3

Lewis Structure

SiH4

8

PH3

8

H2S

8

HCI

8

Si

P

S

Cl

4

Part II, Table 2: Molecular Geometries Central Atom

C

Formula of Hydride

NH3

O

H2O

Si

P

S

Cl

# of Lone Electron Pairs 0

Electron Pair Geometry Tetrahedral

Molecular Shape Tetrahedral

Bond Angle(s)

3

1

Tetrahedral

Pyramidal

107 degrees

2

2

Tetrahedral

Bent shape

105 degrees

1

3

Tetrahedral

Linear

180 degrees

4

0

Tetrahedral

Tetrahedral

110 degrees

3

1

Tetrahedral

T-shaped

91 degrees

2

2

Tetrahedral

V-shaped

92 degrees

1

3

Tetrahedral

Linear

180 degrees

110 degrees

CH4

N

F

# of Bonded Electron Pairs 4

HF

SiH4

PH3

H2 S

HCI

Part II. Fluorinated Compounds Table 3: Fluorinated compounds Molecule

Total # of E.

# Of Bonding

Pairs around

Electron Pairs

# of Lone Pairs

Electron Pair

Molecular

Bond

Geometry

Geometry

Angle(s)

Central Atom 5

5

0

Trigonal pyramid

Trigonal

PF5

90, 180, and 120

5

4

1

Trigonal

Seesaw

SF4

degrees 90, 120, and 180

5

3

2

Trigonal

T-shaped

degrees 90, 120

and 180

CIF3

6

6

0

Octahedral

Octahedral

degrees 90

6

5

1

Octahedral

Square pyramid

degrees 90

SF6 BrF5

6

4

2

Octahedral

Square planar

180

XeF4

4 NF3

degrees 90 and

3

2

Tetrahedral

Trigonal

degrees Less than 102 degrees

Part III: Hydrocarbons Table 4: Hydrocarbons

NAME

FORMULA

Methane

CH4

Ethane

C2 H6

Propane

C3 H8

Butane (structure 1)

C4H10

Butane (structure 2)

C4H10

LEWIS STRUCTURE

DISCUSSION QUESTIONS Part I: Hydrides and Periodicity 1. List the compounds that have similar molecular geometries. CH4 and SiH4 (Tetrahedral) NH3 and PH3 (Trigonal pyramidal) H2O and H2S (Bent) HF and HCI (Linear)

2. How can you relate the molecular geometries of these hydrides to the identities of the central atoms in these compounds?

It is all circumstantial to the amount of pairs / lone pairs a compound has, that determines like geometric similarities.

Part II. Fluorinated Compounds 1. How many different molecular geometry are represented in these compounds?

4 different molecular geometry examples are represented in the above molecular shape lab.

2. Nitrogen and phosphorus are in the same group in the periodic table, but their fluorine-containing compounds have distinctly different stoichiometries and molecular shapes. Provide an explanation for this. Although nitrogen and phosphorus are in the same group in the periodic table, N does not form with PF5. The stoichiometric coefficients of N and P are different because N can form N2 and P can form P4. Resulting in N2 reacting with F2 to form NF3.

Part III: Hydrocarbons 1. What is the bond angle between the first, second and third carbon atoms in propane? 109.5 degrees. They form the tetrahedral Electron Pair Geometry.

2. What is the bond angle between the first, second and third carbon atoms in the first structure of butane? 109.5 degrees; They form the tetrahedral Electron Pair Geometry. 3. Are the bond angles you reported in Questions 1 and 2 the same? Explain why or why not.

Yes, because both have a bond angle of 109.5 degrees forming a tetrahedral EPG.

4. The two structures of butane whose models you built are called isomers. They have the same molecular formula but different arrangements of bonds in their structures. As a

result, they can have different chemical and physical properties. Below, draw the Lewis structures of all of the isomers of pentane, C 5H12. N-Pentane:

Neo-Pentane:

Iso-Pentane:...