Lab 2 Bond Polarity & HydrocarbonsPurpose· In this exercise we will investigate bond polarity and the structure of various types of hydrocarbons. You will investigate how to draw them, how to...

This assigment is due tomorow morning pacific time at 11:59 am


Lab 2 Bond Polarity & Hydrocarbons Purpose · In this exercise we will investigate bond polarity and the structure of various types of hydrocarbons. You will investigate how to draw them, how to interpret them and how different structural representations of chemicals look different or similar. · We will continue to explore the concept of isomers, adding additional types of isomers to our vocabulary including cis and trans isomers that only exist in alkenes due to the double bond structure. Learning objectives are: · Convert between Lewis Structures, Skeletal Structures and Structural Formulas · Distinguish between Skeletal Structures, Structural Formulas and Lewis Structures. · Predict what constitutional isomers are possible for a compound with a given chemical formula. · Differentiate between a 2D representation of a molecule and the actually 3D arrangement of atoms in the molecule. · Use electronegativity differences between atoms in a bond to determine bond polarity · Use bond polarity and VSEPR (Valence Shell Electron Pair Repulsion) shape to determine molecular polarity. Knowledge This assignment will help you review & strengthen knowledge on the following content: · Electronegativity and Polarity · Valence electrons and VSEPR (Valence Shell Electron Pair Repulsion) theory · Isomers Skills After this assignment you should be able to: a. Differentiate between Lewis Structures, Structural Formulas, Condensed Structural Formulas & Skeletal Formulas b. Make predictions about what isomers of a chemical formula will form. c. Identify electronegativity, bond polarity and molecular polarity. d. Differentiate between isomers and the same molecule viewed from a different perspective or using a different structural representation. Criteria for Passing Grade In order to achieve a passing grade student must do the following as a minimum: · Make detailed observations during the completion of the procedure above. · Answer all of the questions using detailed, complete answers with clear reasoning and evidence used as necessary to support your answer. · Complete all answers in their own words. · It is recommended to compare your lab results with other lab teams. Just be sure all your answers are your own original thoughts and in your own words. Activity 1 Introduction In this first activity we will investigate bond polarity, note that this may be different from the molecular polarity. We will explore why in a later exercise. How to Complete Activity 1 Table 1 In order to determine bond polarity you will need to: · look up the electronegativity of each atom in the bond · subtract the smaller electronegativity from the larger one (if they are not equal) to determine the electronegativity difference · use the electronegativity difference to determine the type of bond and its polarity: · <0.5 electronegativity="" difference="" is="" a="" nonpolar="" covalent="" bond(approximately="" equal="" sharing="" of="" electrons)="" ·="">0.5-1.9 is a polar covalent bond (unequal sharing of electrons) · >1.9 is an ionic bond (the more electronegative atom takes the valence electrons from the less electronegative atom resulting in two charged ions attracted to one another by their opposing charge) · Fill in the table below with the data you collect · Activity 1 Table 1 - Fill in the blanks Bonding Pair Electronegativity Difference Type of Bond Bond Polarity H and H ex. 2.1 - 2.1 = 0 ex. covalent ex. non-polar bond B and F C and H N and H H and O O and O C and O Fe and O Na and Cl How to Complete Activity 1 Table 2 1. Step One: Identify the VSEPR (Valence Shell Electron Pair Repulsion) Shape of the Molecule. This will be important, because the shape can impact the overall polarity of the molecule causing the molecular polarity to sometimes differ from the individual bond polarities. a. Build the molecular model using your physical model kit or an online modeling software like https://molview.org or https://chemagic.org/molecules b. Watch this video to review from Chem 121 how to determine VSEPR shapes to determine the shape of your molecule c. Enter your answers in the table below 2. Step Two: Determine the Electronegativity of Each Bond a. Repeat the process you used to determine electronegativity difference in Activity 1 Table 1. b. Enter your answer in the table below 3. Step Three: Determine the Polarity of Each Bond (note for duplicate bonds just list this one time, ie in carbon dioxide there are two identical C-O bonds so you only need to list this once) a. Repeat the process you used to determine bond polarity in Activity 1 Table 1. 4. Step Four: Molecular Polarity - this is where stuff gets interesting!! a. Check out this video for a super simple way to tell if a molecule is polar. b. Check out this video if you’d like to understand more about WHY a molecule is polar or nonpolar. c. Take what you learned to determine the molecular polarity of each molecule below and enter your answer in the table below. Table 2 - fill in the blanks Molecule VSEPR Shape Electronegativity of Each Bond Bond Polarity Molecular Polarity CH4 ex. tetrahedral ex. C-H bond 2.5-2.1= 0.4 ex. Non-polar ex. Non-polar NH3 H2O BeF2 Note this is an Octet Rule Exception BCl3 Note this is an Octet Rule Exception CO2 H2CO Observation Questions 1. Are the molecular and bond polarities always the same for a given molecule? Include an explanation of why or why not in your answer for it to be considered complete. A simple yes or no isn’t sufficient to answer this question. 2. What did you notice about the relationship between lone pairs on the central atom and molecular polarity? 3. What did you notice about the uniformity of the types of atoms around the central atom and its relationship to molecular polarity? Activity 2 How to Complete Activity 2 Table 1 1. Step One: Identify the VSEPR (Valence Shell Electron Pair Repulsion) Shape around the central atoms in each molecule using the same method you used in Activity 1. Be sure to build the model to help with the later parts of this activity. 2. Identify if the C-C bonds can rotate in each molecule (without breaking bonds) or not, use the models you built to help you with this if you’re not sure. 3. Rank the relative total strength of each of the following from least to greatest: single C-C bond, double C-C bond and triple C-C bonds. Hint: think about the total strength of each bond type. 4. Rank the relative chemical reactivity of each of the following from least to greatest: single C-C bond, double C-C bond and triple C-C bonds. Hint: think about what happens when more electrons come into close proximity to one another. 5. Record your answers in the table below. Activity 2 Table 1 - fill in the blanks Example Structural Formula VSEPR Shape Do Bonds Rotate? Relative Bond Strength Relative Bond Reactivity Ethane C2H6 Ethene C2H4 Ethyne C2H2 Observation Questions 4. What are the similarities and differences between alkanes, alkenes and alkynes? 5. How do the differences between alkanes, alkenes and alkynes impact the VSEPR shapes present in each molecule type? 6. How do the differences between alkanes, alkenes and alkynes impact the way they react or behave chemically? Activity 2 - Isomers Table 2 - Fill in the blanks Alkenes: Isomers of C4H8 Molecule 1 Molecule 2 Molecule 3 Structural Formula Condensed Structural Formula ex. CH2=CHCH2CH3 Skeletal Model ex. Observation Questions: 7. Can Molecule 1 be made to look exactly like Molecule 2 without breaking any bonds? Why or why not? 8. Describe the differences in structures between the three alkenes. 9. Are Molecules 1, 2 and 3 chemically identical? Activity 2 - Isomers Table 3 Alkynes Draw all the isomers of the following that contain a C-C triple bond: C4H6 Aromatic Compounds Benzene 10. Are these benzene molecules isomers, or are they the same molecule? Explain. 11. In image 2 above, what is symbolized by the circle in the center? Why does this representation of benzene most accurately represent the actual structure of benzene? Explain your answer. Skeletal Models of Dibromobenzene 12. Are these dibromobenzene molecules isomers, or are they the same molecule? Explain.