exam review packet

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i need someone who is really good in Chem to solve the questions

FINAL EXAM REVIEW PACKET – CHEM 151 – Sec 006/009 – Fall 2017 Name: __________________________________________ UA NetID: ___________________________________@email.arizona.edu Experimental data for ethanol and methanol: METHANOL – 32 g/mol 37.49% C, 12.58% H, 49.93% O IR: C-H, C-O, O-H ETHANOL – 46 g/mol 52.14% C, 13.13% H, 34.73% O IR: C-C, C-H, C-O, O-H 1. Which compound is more volatile? _____________ 2. What is the normal boiling point of each compound? Methanol _____ Ethanol _____ 3. Draw the Lewis structures of methanol and ethanol 4. Explain the differences in volatility by comparing the intermolecular forces. 5. Which compound can exist as a gas at 65 ºC and 0.8 atm? _________________ 6. Predict the elution order of methanol and ethanol on a GC column shown below. Unknown compound data: 44 40.44% C, 7.92% H, 15.72% N, 35.91% O IR: C-C, C-O, C-N, C=O, C-H, O-H, N-H Functional groups: amine, carboxylic acid Solubility: soluble in water (increases with temperature) insoluble in hexane (all temp) 29 15 74 89 7. What is the molecular formula of the unknown compound? ___________________ 8. The compound has a MS fragment at 44 m/z that contains no oxygen atoms. This fragment can be further broken down into 15 m/z and 29 m/z fragments. Draw the Lewis structures of these three MS fragment ions, and the line structure of the full molecule. 9. Draw two PEC diagrams to show how the solubility differs in water and in hexane. 10. Explain why the unknown compound is soluble in water but not in hexane. 11. Draw multiple structures of the unknown compound to show IMFs in a pure liquid. 12. Draw the Lewis structures of the following polyatomic ions. Include resonance structures, if applicable. Predict which of these ions would be soluble in water. Carbonate: CO32- Nitrate: NO3- Sulfate: SO42- Phosphate: PO43- Acetate: CH3CO2- Chlorate: ClO3- Ammonium: NH4+ Hydronium: H3O+ Methenium: CH3+ 13. Sulfate is generally soluble in water while phosphate and carbonate are not, despite all three anions having similar composition. Propose an explanation for this observation. 14. Lithium fluoride is insoluble in water (3 mg/mL at 25 ºC, 1 mg/mL at 30 ºC), while potassium fluoride is soluble in water (949 mg/mL at 25 ºC, 1082 mg/mL at 30 ºC). Draw two PEC diagrams (one for each ionic compound) to illustrate these differences in solubility. 15. Despite differences in solubility, the melting point of lithium fluoride is similar to potassium fluoride. What does that say about the lattice energies of both compounds? 16. Draw the submicroscopic representation of an ionic solid and the hydrated ions. 17. Explain the differences in solubility of lithium fluoride and potassium fluoride using the model above. (Hint: think about the ionic interactions and the hydration interactions in terms of strength and number of configurations, and relate it to ionic size and charge). 18. How would you expect the melting point and the solubility of magnesium fluoride to differ in comparison to lithium fluoride and potassium fluoride? Explain your reasoning. 19. Which compound would have the higher melting point? Which would be more soluble in water? Explain your reasoning. NaCl vs NaBr CaF2 vs KF AlF3 vs CaO 20. Which compound would have the higher boiling point? Explain your reasoning. 21. Which of the following would have the larger atomic (or ionic) radius? F- vs F F- vs Na+ Na+ vs K+ K+ vs Ca2+ Ca2+ vs Ca 22. Which of the compounds below are polar? (i.e. have a permanent molecular dipole) H F Br N Br H S C O O Cl C F Cl A substitution reaction is shown: Label the activation energy for the forward reaction and the reverse reaction. 23. Which reaction is endothermic? a. forward b. reverse c. both d. neither 24. Which reaction is favored in terms in terms of activation energy? Explain. 25. Which reaction is favored in terms of configurational effectiveness? Explain. 26. A catalyst can speed up the reaction by stabilizing the transition state. Draw the reaction coordinate diagram for a catalyzed reaction relative to an uncatalyzed reaction. 27. A change in the solvent from a polar (acetone) to a nonpolar (hexane) actually makes the forward reaction endothermic without affecting the transition state. Draw the reaction coordinate diagram for the reaction in a nonpolar solvent relative to a polar solvent. 28. The C-Br bond is stronger than the C-I bond. Based on these bond energies, would you predict the forward reaction to be endothermic or exothermic? How do you think the solvent polarity would affect the thermodynamic properties of the reaction? (Hint: think about how a polar solvent would interact with I- and Br- anions). Potassium metal reacts violently with water to produce aqueous potassium hydroxide and hydrogen gas. The UNBALANCED equation is given below: K(s) + H2O(l) à KOH(aq) + H2(g) [ΔH = -196 kJ/mole of potassium] 29. Balance the equation above. 30. Is the reaction endothermic or exothermic? 31. If the activation energy is 508 kJ/mol for the forward reaction. What is the activation energy for the reverse reaction? (Hint: draw a reaction coordinate diagram) 32. Does the reaction favor reactants or products? To what extent? 33. If 10 g of potassium metal was added to an excess amount of water… a. how many molecules of H2O would be consumed to react with all of the potassium? b. how many liters of hydrogen gas would be produced? (hint: use ideal gas law at STP) c. how much energy (in kJ) would be absorbed or released? 34. The potassium reaction is so energetic that the hydrogen gas combusts with the oxygen in the atmosphere. Write out the balanced chemical equation for this process. 35. Based on bond energies [H-H 436 kJ/mol, O=O 498 kJ/mol, O-H 460 kJ/mol], determine ΔΗ for the above reaction. Is it endothermic or exothermic? 36. The combustion of hydrogen also excites the hydrogen atoms, which emit light at 626 nm. What is the energy (in kJ/mol) of the photons emitted? 37. If 4 g of hydrogen gas reacts with 12 g of oxygen gas, which would be the limiting reactant? How many grams of water would be produced? 38. Bond formation (though delocalization of bonding electrons) releases energy. Explain this phenomenon in terms of potential energy and kinetic energy of the electrons. 39. Draw a phase diagram for water (or look it up). 40. What happens to the kinetic energy of H2O molecules when solid ice is gradually heated from -40 ºC to 0 ºC at 1 atm? What about the potential energy? Explain why. 41. What happens to the kinetic energy of H2O molecules when solid ice melts at 0 ºC and 1 atm? What about the potential energy? Explain why. 42. What happens to the kinetic energy of H2O molecules when water vapor is compressed from 1 atm to 10 atm at 120 °C? What about the potential energy? Explain. 43. What is the difference between the internal potential energy (within the molecule) and the potential energy of interactions (between molecules)? Which of the two best relates to the potential energy of the electrons in the Bohr model? 44. Draw the photoelectron spectrum (PES) of oxygen and of carbon, relative to each other. Why does oxygen usually form 2 bonds, while carbon usually forms 4 bonds? 45. Although oxygen has 6 valence electrons, it does not form 6 bonds. On the other hand, sulfur also has 6 valence electrons but can form 6 bonds. Explain this observation. Lidocaine structure is shown to the right Solubility - very soluble in acetone - somewhat soluble in hexane - insoluble in water 46. Explain the trends in solubility of lidocaine in the different solvents mentioned above. Lidocaine is used as a local anesthetic – it disrupts sodium channels that generate the action potential (nerve impulses). The interaction of lidocaine and the sodium channel is shown below (sodium channel not drawn to scale). 47. What are the main types of intermolecular interactions present between lidocaine and the amino acids in the sodium channel? Benzocaine structure is shown below 48. Lidocaine interacts with the sodium channel about 5 times stronger than benzocaine. Explain this observation. 49. Benzocaine is more soluble in water than lidocaine. Explain this observation. 50. What is the molecular geometry of the nitrogen atom in benzocaine? What about the carbons in the ring? What about the oxygen in between two carbons? A rock weighing 10 g is heated to 40 °C (Trock = 40 °C). It is then added to a beaker filled with 10 g of water (Twater = 20 °C). This system (rock + water) is isolated from the surroundings, such that no heat can be added to or removed from the system. After 30 minutes, the temperature of the system is measured – both the rock and the water are at 24 °C. 51. Why did the temperature of the rock decrease (40 °C à 24 °C), while the temperature of the water increased (20 °C à 24 °C)? Explain this heat transfer in terms of kinetic energy. 52. Although one may predict the final temperature to be 30 °C (average of 20 °C and 40 °C, since both components – rock and water – had the same mass), the experiment shows that the temperature of water did not change as much as the temperature of the rock. What does that say about the potential energy of the rock compared to that of water? 53. Consider a reaction of the particles of air (nitrogen, oxygen, carbon dioxide). Write out the balanced chemical equation for this process (including phases). Be sure to identify the limiting reactant. (black: N, white: O, gray: C) 54. Write out the full electron configuration of various magnesium atoms shown below. Mg Mg+ Mg+2 Mg+3 Mg+4 55. How would you expect the first ionization energy to differ for the atoms above? (i.e. would it require more or less energy to remove the outermost electron from each atom?) Why? 56. What is the most stable ionic state of magnesium? Explain using the answer above. 57. What is the difference between melting and dissolving? What happens when you put a piece of chocolate in your mouth - does it melt or dissolve? Are both processes always endothermic?

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